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CVE-2023-20177: Cisco Security Advisory: Cisco Firepower Threat Defense Software SSL/TLS URL Category and Snort 3 Detection Engine Bypass and Denial of Service Vulnerability

A vulnerability in the SSL file policy implementation of Cisco Firepower Threat Defense (FTD) Software that occurs when the SSL/TLS connection is configured with a URL Category and the Snort 3 detection engine could allow an unauthenticated, remote attacker to cause the Snort 3 detection engine to unexpectedly restart. This vulnerability exists because a logic error occurs when a Snort 3 detection engine inspects an SSL/TLS connection that has either a URL Category configured on the SSL file policy or a URL Category configured on an access control policy with TLS server identity discovery enabled. Under specific, time-based constraints, an attacker could exploit this vulnerability by sending a crafted SSL/TLS connection through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 detection engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. The Snort 3 detection engine will restart automatically. No manual intervention is required.

CVE
Open in Source
#vulnerability#web#ios#cisco#dos#perl#botnet#auth#ssl

Cisco Firepower Threat Defense Software SSL/TLS URL Category and Snort 3 Detection Engine Bypass and Denial of Service Vulnerability

Medium

CVE-2023-20177

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**

Summary

**

  • A vulnerability in the SSL file policy implementation of Cisco Firepower Threat Defense (FTD) Software that occurs when the SSL/TLS connection is configured with a URL Category and the Snort 3 detection engine could allow an unauthenticated, remote attacker to cause the Snort 3 detection engine to unexpectedly restart.

    This vulnerability exists because a logic error occurs when a Snort 3 detection engine inspects an SSL/TLS connection that has either a URL Category configured on the SSL file policy or a URL Category configured on an access control policy with TLS server identity discovery enabled. Under specific, time-based constraints, an attacker could exploit this vulnerability by sending a crafted SSL/TLS connection through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 detection engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. See the Details section of this advisory for more information. The Snort 3 detection engine will restart automatically. No manual intervention is required.

    Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

    This advisory is available at the following link:
    https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sa-ftd-snort3-urldos-OccFQTeX

    This advisory is part of the November 2023 release of the Cisco ASA, FTD, and FMC Security Advisory Bundled publication. For a complete list of the advisories and links to them, see Cisco Event Response: November 2023 Semiannual Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.

**

Affected Products

**

  • At the time of publication, this vulnerability affected Cisco FTD Software if it was running a vulnerable release and met all of the following conditions:

    • The device was running Snort 3.
    • The device had at least one of the following configurations:
      • An SSL policy with a URL category configured.
      • An access control policy with TLS server identity discovery enabled and a URL category configured.

    For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

    Determine Cisco FTD Software Snort Configuration

    To determine whether Snort 3 is running on Cisco FTD Software, see Determine the Active Snort Version that Runs on Firepower Threat Defense (FTD). Snort 3 must be active for this vulnerability to be exploited.

    Determine Cisco FTD Software SSL Policy Configuration

    SSL decryption policies are not configured by default.

    Determine Cisco FTD Software SSL Policy Configuration Using the FTD Software CLI

    To determine whether an SSL policy is configured on a device that is running Cisco FTD Software, log in to the Cisco FTD Software CLI and use the show ssl-policy-config command.

    If the command output shows SSL policy not yet applied, the device might not be affected by this vulnerability, as shown in the following example:

    >show ssl-policy-config
    SSL policy not yet applied

    If the command output shows a policy, the device has an SSL policy applied and could be affected by this vulnerability, as shown in the following example:

    > show ssl-policy-config
    ===================[ CSCwe87591 ]===================
    =================[ Default Action ]=================
    Default Action : Do Not Decrypt
    …

    Determine Cisco FTD Software SSL Policy Configuration for Devices that Are Managed by Cisco Firepower Device Manager Software

    To determine whether an SSL policy is configured on a device that is managed by Cisco Firepower Device Manager (FDM) Software, complete the following steps:

    1. Log in to the Cisco FTD Software web interface.
    2. From the main menu, choose Policies.
    3. Choose the SSL Decryption tab.
    • If SSL decryption is not enabled, the device might not be affected by this vulnerability.
    • If a Policy Name is listed, the device has an SSL policy applied and could be affected by this vulnerability.

    For detailed information about SSL decryption policies, see the SSL Decryption chapter of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Determine Cisco FTD Software SSL Policy Configuration for Devices that are Managed by Cisco Firepower Management Center Software

    To determine whether an SSL policy is configured on a device that is managed by Cisco Firepower Management Center (FMC) Software, complete the following steps:

    1. Log in to the Cisco FMC Software web interface.
    2. From the Policies menu, choose Access Control.
    3. Choose the appropriate Access Control Policy.
    4. Click the Edit pencil icon.
    5. Look in the SSL Policy area.
      • If None is listed, the device might not be affected by this vulnerability.
      • If a Policy Name is listed, the device has an SSL policy applied and could be affected by this vulnerability.

    For detailed information about SSL decryption policies, see the SSL Policy chapter of the Cisco Secure Firewall Management Center Configuration Guide.

    Determine Cisco FTD Software SSL Policy Configuration for Devices that are Managed by Cisco Defense Orchestrator

    To determine whether an SSL policy is configured on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

    1. Log in to the Cisco Defense Orchestrator web interface.
    2. From the Cisco Defense Orchestrator Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Access Control.
    4. Choose the appropriate Access Control Policy.
    5. Click the Edit pencil icon.
    6. Look in the Decryption area.
    • If None is listed, the device might not be affected by this vulnerability.
    • If a Policy Name is listed, the device has an SSL policy applied and could be affected by this vulnerability.

    For detailed information about devices managed by Cisco Defense Orchestrator, see the Cisco Defense Orchestrator documentation.

    For detailed information about SSL decryption policies for Cisco FMC Devices managed with Cisco Defense Orchestrator, see the Decryption Policies chapter of Managing Firewall Threat Defense with Cloud-delivered Firewall Management Center in Cisco Defense Orchestrator.

    For detailed information about SSL decryption policies for Cisco FDM Devices managed with Cisco Defense Orchestrator, see the SSL Decryption Policy section of Managing FDM Devices with Cisco Defense Orchestrator.

    Determine Cisco FTD Software SSL Policy URL Category Configuration

    URL Categories in the SSL policy are not configured by default.

    Determine Cisco FTD Software SSL Policy URL Category Configuration Using the FTD Software CLI

    To determine whether a URL category for the SSL policy is configured on a device by using the CLI, log in to the Cisco FTD Software CLI and use the grep url /ngfw/var/sf/detection_engines/*/ssl/ssl.rules command.

    If the command output shows url_categories (any), the device might not be affected by this vulnerability, as shown in the following example:

    > expert
    admin@ftd:~$
    admin@ftd:~$grep url /ngfw/var/sf/detection_engines/*/ssl/ssl.rules url_categories (any);

    If the command output shows url_categories (string of numbers), the device has an SSL policy with a URL category configured and is affected by this vulnerability, as shown in the following example:

    > expert
    admin@ftd:~$
    admin@ftd:~$grep url /ngfw/var/sf/detection_engines/*/ssl/ssl.rules
    url_categories (2107:0:0,2107:1:100);

    Determine Cisco FTD Software SSL Policy URL Category Configuration for Devices that are Managed by Cisco FDM Software

    To determine whether a URL Category is configured on a device that is managed by Cisco FDM software, complete the following steps:

    1. Log in to the Cisco FTD Software web interface.
    2. From the main menu, choose Policies.
    3. Choose the SSL Decryption tab.
    4. For each rule configured, look in the URLs column.
    • If the value in that column is ANY, the device might not be affected by this vulnerability.
    • If the value in that column has any other value, the device has an SSL policy with URL category configured and is affected by this vulnerability.

    For detailed information about URL Categories, see the URL Criteria for SSL Decryption Rules section in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    For detailed information about URL filtering, see the URL filtering section of the Access Control chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Determine Cisco FTD Software SSL Policy URL Category Configuration for Devices that are Managed by Cisco FMC Software

    To determine whether a URL Category is configured on a device that is managed by Cisco FMC Software, complete the following steps:

    1. Log in to the FMC Software web interface.
    2. From the Policies menu, choose SSL.
    3. Choose the appropriate SSL Policy.
    4. Click the Edit pencil icon.
    5. For each rule configured, look in the Categories column.
    • If the value in that column is any, the device might not be affected by this vulnerability.
    • If the value in that column has any other value, the device has an SSL policy with URL category configured and is affected by this vulnerability.

    For detailed information about URL Categories, see the Category Rule Conditions section in the Cisco Secure Firewall Management Center Configuration Guide.

    For detailed information about URL filtering, see the URL filtering section of the Access Control chapter in the Cisco Secure Firewall Management Center Configuration Guide.

    Determine Cisco FTD Software SSL Policy URL Category Configuration for Devices that are Managed by Cisco Defense Orchestrator

    To determine whether a URL Category is configured on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

    1. Log in to the Cisco Defense Orchestrator web interface.
    2. From the Cisco Defense Orchestrator Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Decryption.
    4. Choose the appropriate Decryption Policy.
    5. Click the Edit pencil icon.
    6. For each rule configured, look in the Categories column.
    • If the value in that column is any, the device might not be affected by this vulnerability.
    • If the value in that column has any other value, the device has an SSL policy with URL category configured and is affected by this vulnerability.

    For detailed information about Cisco Defense Orchestrator managed devices, see the Cisco Defense Orchestrator documentation.

    For detailed information about URL Categories, see the Decryption Rules chapter of Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator.

    For detailed information about URL filtering, see the Access Control chapter of Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator.

    For detailed information about URL Categories for Cisco FDM Devices managed with Cisco Defense Orchestrator, see the URL Criteria for SSL Decryption Rules section of Managing FDM Devices with Cisco Defense Orchestrator.

    For detailed information about URL filtering, see the Access Control section of Managing FDM Devices with Cisco Defense Orchestrator.

    Determine Cisco FTD Software TLS Server Identity Discovery Configuration

    TLS server identity discovery is disabled by default.

    Determine Cisco FTD Software TLS Server Identity Discovery Configuration Using the FTD Software CLI

    To determine whether TLS server identity discovery is configured on a device that is running Cisco FTD Software, log in to the Cisco FTD Software CLI and use the show access-control-config command. Scroll down to the Advanced Settings section. If the output shows TLS Server Identity Discovery Enabled, the device could be affected by this vulnerability:

    The following example shows the TLS server identity discovery disabled:

    >**show access-control-config
    **

    ===============[ Advanced Settings ]================

    General Settings

    Maximum URL Length : 1024

    Interactive Block Bypass Timeout : 600

    TLS Server Identity Discovery : Disabled

    The following example shows the TLS server identity discovery enabled:

    > show access-control-config

    ===============[ Advanced Settings ]================

    General Settings

    Maximum URL Length : 1024

    Interactive Block Bypass Timeout : 600

    SSL Policy : Certificate-Visibility-SSL-Policy

    TLS Server Identity Discovery : Enabled

    Note: Due to CSCvz06256, this command will not show the TLS server identity discovery setting for the Cisco FTD 7.0 software train.

    Determine Cisco FTD Software TLS Server Identity Discovery Configuration for Devices Managed by Cisco FDM Software

    To determine whether TLS server identity discovery is configured on a device that is managed by Cisco FDM Software, complete the following steps:

    1. Log in to the Cisco FDM web interface.
    2. From the Policies menu, choose Access Control.
    3. Click on the Settings gear icon.
    4. Locate the TLS Server Identity Discovery setting.
      • If the setting is enabled, the device could be affected by this vulnerability.
      • If the setting is disabled, the device might not be affected by this vulnerability.

    For detailed information about TLS server identity discovery, see the Access Control chapter of Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Determine Cisco FTD Software TLS Server Identity Discovery Configuration for Devices that are Managed by Cisco FMC Software

    To determine whether TLS server identity discovery is configured on a device that is managed by Cisco FMC, complete the following steps:

    1. Log in to the Cisco FMC web interface.
    2. From the Policies menu, choose Access Control.
    3. Choose the appropriate Access Control Policy.
    4. Click the Edit pencil icon.
    5. Click on the Advanced tab.
    6. Locate the TLS Server Identity Discovery setting.
      • If the setting is enabled, the device could be affected by this vulnerability.
      • If the setting is disabled, the device might not be affected by this vulnerability.

    For detailed information about TLS server identity discovery, see the Access Control Policy chapter of Cisco Secure Firewall Management Center Device Configuration.

    Determine Cisco FTD Software TLS Server Identity Discovery Configuration for Devices Managed by Cisco Defense Orchestrator

    To determine whether TLS server identity discovery is configured on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

    1. Log in to the Cisco Defense Orchestrator web interface.
    2. From the Cisco Defense Orchestrator Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Access Control.
    4. Choose the appropriate Access Control Policy.
    5. Click the Edit pencil icon.
    6. Choose More and then Click on then Advanced Settings.
    7. Locate the TLS Server Identity Discovery setting.
      • If the setting is enabled, the device could be affected by this vulnerability.
      • If the setting is disabled, the device might not be affected by this vulnerability.

    For detailed information about TLS server identity discovery, see the Cisco Defense Orchestrator documentation.

    Determine Cisco FTD Software Access Control Policy URL Category Configuration

    URL Categories in the access control policy are not configured by default.

    Determine Cisco FTD Software Access Control Policy URL Category Configuration Using the FTD Software CLI

    Use the show access-control-config command. Scroll down to the Rule section.

    If the output of command does not include a category section, the device might not be affected by this vulnerability, as shown in the following example that shows no URL category configured:

    > show access-control-config

    --------------[ Rule: CSCwe87591_AC ]---------------

    Action : Fast-path

    Source ISE Metadata :

    Source Zones : inside_zone

    Destination Zones : outside_zone

    Users

    URLs

    Logging Configuration

    If the output of command shows Category: any value, the device could be affected by this vulnerability, as shown in this example with URL category configured:

    > show access-control-config

    --------------[ Rule: CSCwe87591_AC ]---------------

    Action : Fast-path

    Source ISE Metadata :

    Source Zones : inside_zone

    Destination Zones : outside_zone

    Users

    URLs

    Category : Botnets

    Reputation : Unknown

    Logging Configuration

    Determine Cisco FTD Software Access Control Policy URL Category Configuration for Devices that are Managed by Cisco FDM

    To determine whether an access control policy URL category is configured on a device that is managed by Cisco FDM, complete the following steps:

    1. Log in to the Cisco FTD Software web interface.
    2. From the main menu, choose Policies.
    3. Choose the Access Control tab.
    4. For each rule configured, look in the URLs column.
    • If the value in that column is ANY, the device might not be affected by this vulnerability.
    • If the value in that column has any other value, the device could be affected by this vulnerability.

    For detailed information about access control policy URL categories, see the Access Control chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Determine Cisco FTD Software Access Control Policy URL Category Configuration for Devices that are Managed by Cisco FMC Software

    To determine whether an access control policy URL category is configured on a device that is managed by Cisco FMC Software, complete the following steps:

    1. Log in to the Cisco FMC Software web interface.
    2. From the Policies menu, choose Access Control.
    3. Choose the appropriate Access Control Policy.
    4. Click the Edit pencil icon.
    5. For each rule configured, look in the URLs column.
    • If the value in that column is Any, the device might not be affected by this vulnerability.
    • If the value in that column has any other value, the device could be affected by this vulnerability.

    For detailed information about access control policy URL categories, see the Access Control chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Determine Cisco FTD Software Access Control Policy URL Category Configuration for Devices that are Managed by Cisco Defense Orchestrator

    To determine whether an access control policy URL category is configured on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

    1. Log in to the Cisco Defense Orchestrator web interface.
    2. From the Cisco Defense Orchestrator Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Access Control.
    4. Choose the appropriate Access Control Policy.
    5. Click the Edit pencil icon.
    6. For each rule configured, look in the URLs column.
    • If the value in that column is Any, the device might not be affected by this vulnerability.
    • If the value in that column has any other value, the device could be affected by this vulnerability.

    For detailed information about devices that are managed by Cisco Defense Orchestrator, see the Cisco Defense Orchestrator documentation.

    For detailed information about access control policy URL categories, see the Access Control chapter of Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator.

    For detailed information about access control policy URL Categories, see the Access Control section of Managing FDM Devices with Cisco Defense Orchestrator.

    Cisco has confirmed that this vulnerability does not affect the following products:

    • Cisco Adaptive Security Appliance (ASA) Software
    • Cisco FMC Software
    • Open Source Snort 2
    • Open Source Snort 3

**

Details

**

  • The following Cisco FTD Software Snort 3 configuration parameters govern how traffic is handled if the Snort 3 process restarts, which could change how encrypted traffic is handled during an exploit of this vulnerability.

    • Snort Fail Open
    • Snort preserve-connection

    For additional information, see the Snort Restart Traffic Behavior section of the Firepower Management Center Configuration Guide or the Managing Firewall Threat Defense with Cloud-delivered Firewall Management Center in Cisco Defense Orchestrator guide.

**

Indicators of Compromise

**

  • An indication that this vulnerability might have been exploited is if specific Snort 3 counters have been incremented. The administrator can issue the show snort counters CLI command and look for non-zero values for rules_url_retry and/or cache_original_expire.

    # **show snort counters
    **.
    .
    .
    rules_url_retry: 1676
    cache_original_expire: 124
    .
    .
    .

    These counters can increment for other conditions as well. If further assistance is needed, contact the Cisco Technical Assistance Center (TAC).

**

Workarounds

**

  • There is a workaround and mitigations that address this vulnerability. To remove the attack vector for this vulnerability, do one of the following:

    • Revert to Snort 2.

    • Remain on Snort 3 but ensure that neither of the following is configured:

    • An SSL policy with a URL category configured.

    • An Access Control policy with TLS Server Identity Discovery enabled and a URL category configured.

    Note: A Decryption policy or SSL policy does not need to be configured and associated with the Access Control policy for TLS Server Identity Discovery to be enabled.

    Revert to Snort 2

    Before downgrading, review the Before you Begin section in the Switching Between Snort 2 and Snort 3 section of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Note: Downgrading to Snort 2 will delete customer policies, NAP customizations, and Hostname redirect in active authentications. To discuss the effects of reverting on the deployment, contact the Technical Assistance Center (TAC)

    Revert to Snort 2 for Cisco FTD devices by using the CLI

    There is no option to change this configuration by using the CLI.

    Revert to Snort 2 for Cisco FTD devices that are managed by FDM Software

    To revert to Snort 2 on a device that is managed by Cisco FDM Software, complete the following steps:

    1. Log in to the Cisco FTD Software web interface.
    2. From the main menu, choose Device.
    3. In the Updates area, choose View Configuration.
    4. In the Intrusion Rule section, choose Downgrade to 2.0.

    After making the changes above, deploy changes to your Cisco FTD devices.

    For detailed information about reverting to Snort 2, see the Switching Between Snort 2 and Snort 3 section of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Revert to Snort 2 for Cisco FTD devices that are managed by FMC Software

    To revert to Snort 2 on a device that is managed by Cisco FMC Software, complete the following steps:

    1. Log in to the Cisco FMC Software web interface.
    2. From the Devices menu, choose Device Management.
    3. Choose the appropriate Cisco FTD device.
    4. Click the Edit pencil icon.
    5. Choose the Device tab.
    6. In the Inspection Engine area, choose Revert to Snort 2.

    After making the changes above, deploy changes to your Cisco FTD devices.

    For detailed information about reverting to Snort 2, see the Snort 3 Inspection Engine chapter of the Cisco Secure Firewall Management Center Snort 3 Configuration Guide.

    Revert to Snort 2 for Cisco FTD devices managed by Cisco Defense Orchestrator

    To revert to Snort 2 on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

    1. Log in to the Cisco Defense Orchestrator web interface.
    2. In the navigation bar, click Inventory.
    3. Click the Devices tab.
    4. Click the FTD tab and click the device you want to revert.
    5. In the Device Actions pane located to the right, click Upgrade.
    6. Set the upgrade toggle to Intrusion Prevention Engine.
    7. Click Revert to Snort Engine 2.0.

    After making the changes above, deploy changes to your Cisco FTD devices.

    For detailed information about Cisco Defense Orchestrator managed devices, see the Cisco Defense Orchestrator documentation.

    For detailed information about reverting to Snort 2 for Cisco FMC Devices managed by Cisco Defense Orchestrator, see the Snort 3 Inspection Engine chapter of the Cisco Secure Firewall Management Center Snort 3 Configuration Guide.

    For detailed information about reverting to Snort 2 for Cisco FDM Devices managed with Cisco Defense Orchestrator, see the Revert From Snort 3.0 for FDM-Managed Device section of Managing FDM Devices with Cisco Defense Orchestrator.

    Mitigations for Cisco FDM Managed Devices

    For Cisco FTD devices that stay on Snort 3, both the access control policy and SSL policy must be checked to ensure the device is not affected by this vulnerability. If either place is configured in a vulnerable manner, the device is affected by this vulnerability.

    Access Control Policy

    If the device is using an access control policy with TLS server identity discovery enabled and URL categories configured, the device is affected by this vulnerability. The following options can be used to close the vector of attack:

    1. Disable the TLS server identity discovery and leave the URL categories configured.
    2. Remove the URL categories configuration and leave the TLS server identity enabled.

    SSL Policy

    If the device is using an SSL policy with URL categories configured, the device is affected by this vulnerability. The following options can be used to close the vector of attack:

    1. Remove the URL categories configuration from the SSL policy.
    2. Remove the SSL policy from the access control policy.

    Disable TLS Server Identity Discovery

    Disabling TLS Server Identity Discovery Cisco FTD devices using the CLI

    There is no option to change this configuration using the CLI.

    Disabling TLS Server Identity Discovery Cisco for Devices that are Managed by Cisco FDM Software

    To disable the TLS server identity discovery for Cisco FDM Software-managed devices, do the following:

    1. Log in to the Cisco FDM web interface.
    2. From the Policies menu, choose Access Control.
    3. Click the Settings gear icon.
    4. If the TLS Server Identity Discovery setting is enabled, disable it and click OK.

    After changing the policies above, deploy the new policies to your Cisco FTD devices.

    For more information, see the Access Control Chapter of the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Disabling TLS Server Identity Discovery Cisco for Devices that are Managed by Cisco FMC Software

    To disable the TLS server identity discovery for devices that are managed by Cisco FMC Software, do the following:

    1. Log in to the Cisco FMC web interface.
    2. From the Policies menu, choose Access Control.
    3. Choose the appropriate Access Control Policy.
    4. Click the Edit pencil icon.
    5. Click on the Advanced tab.
    6. Locate the TLS Server Identity Discovery setting.
    7. If the setting is enabled, click the Edit pencil icon.
    8. Uncheck the Early application detection and URL categorization box and choose OK.
    9. Click Save to save the policy.

    After changing the policies above, deploy the new policies to your Cisco FTD devices.

    For more information, see the Access Control Chapter of the Firepower Management Center Device Configuration Guide.

    Disabling TLS Server Identity Discovery Cisco for Devices that are Managed by Cisco Defense Orchestrator

    To disable the TLS server identity discovery for devices managed by Cisco Defense Orchestrator, do the following:

    1. Log in to the Cisco Defense Orchestrator web interface.
    2. From the CDO Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Access Control.
    4. Choose the appropriate Access Control Policy.
    5. Click the Edit pencil icon.
    6. Choose More and then click on then Advanced Settings
    7. Locate the TLS Server Identity Discovery setting.
    8. If the setting is enabled, click the Edit pencil icon.
    9. Uncheck the Early application detection and URL categorization box and choose OK.
    10. Click Save to save the policy

    After changing the policies above, deploy the new policies to your Cisco Defense Orchestrator devices.

    For more information, see the Cisco Defense Orchestrator documentation.

    For detailed information about TLS server identity discovery for Cisco FMC Devices managed with Cisco Defense Orchestrator, see the Access Control Policies chapter of Managing Firewall Threat Defense with Cloud-delivered Firewall Management Center in Cisco Defense Orchestrator.

    For detailed information about TLS server identity discovery for Cisco FDM Devices managed with Cisco Defense Orchestrator, see the Configuring FDM-Managed Devices section of Managing FDM Devices with Cisco Defense Orchestrator.

    Removing Access Control Policy URL categories

    Removing Access Control Policy URL categories for Cisco FTD devices using the CLI

    There is no option to change this configuration using the CLI.

    Removing Access Control Policy URL categories for Cisco FTD devices managed by FDM Software

    To disable the Access Control Policy URL Category on a device that is managed by Cisco FDM Software, complete the following steps:

    1. Log in to the Cisco FDM web interface.
    2. From the main menu, choose Policies.
    3. Choose the Access Control tab.
    4. For each rule configured, look in the URLs column.
    5. If there is a category listed, then click on the name of the category.
    6. In the pop-up window, click the X next to the name to remove the category and choose OK.

    After changing the policies above, deploy the new policies to your Cisco FTD devices.

    For detailed information about access control policy URL Categories, see the Access Control chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Removing Access Control Policy URL categories for Cisco FTD devices managed by FMC Software

    To disable the access control policy URL category on a device that is managed by Cisco FMC Software, complete the following steps:

    1. Log in to the Cisco FMC Software web interface.
    2. From the Policies menu, choose Access Control.
    3. Choose the appropriate Access Control Policy.
    4. Click the Edit pencil icon.
    5. For each rule configured, look in the URLs column.
    6. If there is a category listed, then click on the name of the category.
    7. In the pop-up window, click the trash can icon to delete the URL category and choose Save.
    8. Choose Save.

    After changing the policies above, deploy the new policies to your FTD devices.

    For detailed information about access control policy URL categories, see the Access Control chapter in Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Removing Access Control Policy URL categories for Cisco FTD devices managed by Cisco Defense Orchestrator

    To disable the Access Control Policy URL Category on a device that is managed by Cisco Defense Orchestrator, complete the following steps:

    1. Log in to the Cisco Defense Orchestrator web interface.
    2. From the Cisco Defense Orchestrator Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Access Control.
    4. Choose the appropriate Access Control Policy.
    5. Click the Edit pencil icon.
    6. For each rule configured, look in the URLs column.
    7. If there is a category listed, then click on the name of the category.
    8. In the pop-up window, click the X next to the name to remove the category and choose Apply.
    9. Choose Save.

    After changing the policies above, deploy the new policies to your Cisco FTD devices.

    For detailed information about Cisco Defense Orchestrator managed devices, see the Cisco Defense Orchestrator documentation.

    For detailed information about access control policy URL categories, see the Access Control chapter of Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator.

    For detailed information about access control policy URL categories, see the Access Control section of Managing FDM Devices with Cisco Defense Orchestrator guide.

    Removing SSL Policy URL categories

    Removing SSL Policy URL categories for Cisco FTD devices using the CLI

    There is no option to change this configuration using the CLI.

    Removing SSL Policy URL categories for Cisco FTD devices managed by FDM Software

    To remove the SSL policy URL Category configuration on a device that is managed by Cisco FDM Software, complete the following steps:

    1. Log in to the Cisco FDM web interface.
    2. From the main menu, choose Policies.
    3. Choose the SSL Decryption tab.
    4. For each rule configured, look in the URLs column.
    5. If there is a category listed, then click on the name of the category.
    6. In the pop-up window, click the X next to the name of the category to remove the category
    7. Choose OK.

    After changing the policies above, deploy the new policies to your FTD devices.

    For detailed information about URL Categories, see the URL Criteria for SSL Decryption Rules section in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    For detailed information about URL filtering, see the URL filtering section of the Access Control chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Removing SSL Policy URL categories for Cisco FTD devices managed by FMC

    To remove the SSL policy URL Category configuration on a device that is managed by Cisco FMC Software, complete the following steps:

    1. Log in to the Cisco FMC Software web interface.
    2. From the Policies menu, choose SSL.
    3. Choose the appropriate SSL Policy.
    4. Click the Edit pencil icon.
    5. For each rule configured, look in the Categories column.
    6. If there is a category listed, then click on the name of the category.
    7. In the pop-up window, click the trash can icon to delete the URL category and choose Save.
    8. Choose Save.

    After changing the policies above, deploy the new policies to your Cisco FTD devices.

    For detailed information about URL Categories, see the Category Rule Conditions section in the Cisco Secure Firewall Management Center Configuration Guide.

    For detailed information about URL filtering, see the URL filtering section of the Access Control chapter in the Cisco Secure Firewall Management Center Configuration Guide.

    Removing SSL Policy URL categories for Cisco FTD devices managed by Cisco Discovery Orchestrator

    To remove the SSL policy URL Category configuration on a device that is managed by Cisco Discovery Orchestrator, complete the following steps:

    1. Log in to the Cisco Discovery Orchestrator web interface.
    2. From the Cisco Discovery Orchestrator Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Decryption.
    4. Choose the appropriate Decryption Policy.
    5. Click the Edit pencil icon.
    6. For each rule configured, look in the URL column.
    7. If there is a category listed, then click on the name of the category.
    8. In the pop-up window, click the trash can icon to remove the category and choose Save.
    9. Choose Save.

    After changing the policies above, deploy the new policies to your Cisco FTD devices.

    For detailed information about Cisco Discovery Orchestrator managed devices, see the Cisco Defense Orchestrator documentation.

    For detailed information about URL categories, see the Decryption Rules chapter of the Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator guide.

    For detailed information about URL filtering, see the Access Control chapter of the Managing Firewall Threat Defense with Cloud-Delivered Firewall Management Center in Cisco Defense Orchestrator guide.

    For detailed information about URL categories for Cisco FDM Devices managed with Cisco Discovery Orchestrator, see the URL Criteria for SSL Decryption Rules section of Managing FDM Devices with Cisco Defense Orchestrator.

    For detailed information about URL filtering, see the Access Control section of Managing FDM Devices with Cisco Defense Orchestrator.

    Removing SSL Policy from Access Control Policy

    Removing SSL Policy from Access Control Policy for Cisco FTD Devices Using the CLI

    There is no option to change this configuration using the CLI.

    Removing SSL Policy from Access Control Policy for Cisco FTD Devices Managed by FDM Software

    To remove the SSL policy URL category configuration on a device that is managed by Cisco FDM Software, complete the following steps:

    1. Log in to the Cisco FDM web interface.
    2. From the main menu, choose Policies.
    3. Choose the SSL Decryption tab.
    4. If SSL Decryption is enabled, disable it.

    After changing the policies above, deploy the new policies to your FTD devices.

    For detailed information about SSL Decryption, see the SSL Decryption chapter in the Cisco Firepower Threat Defense Configuration Guide for Firepower Device Manager.

    Removing SSL Policy from Access Control Policy for Cisco FTD Devices Managed by FMC

    To remove the SSL policy URL category configuration on a device that is managed by Cisco FDM Software, complete the following steps:

    1. Log in to the Cisco FMC Software web interface.
    2. From the Policies menu, choose Access Control.
    3. Choose the appropriate Access Control Policy.
    4. Click the Edit pencil icon.
    5. Look in the SSL Policy area.
    6. If a Policy Name is listed, click on the name.
    7. In the pop-up window, choose None from the drop-down menu and choose OK.
    8. Choose Save.

    After changing the policies above, deploy the new policies to your FTD devices.

    For detailed information about SSL decryption policies, see the SSL Policy chapter of the Cisco Secure Firewall Management Center Configuration Guide.

    Removing SSL Policy from Access Control Policy for Cisco FTD Devices Managed by Cisco Discovery Orchestrator

    To remove the SSL policy URL category configuration on a device that is managed by Cisco Discovery Orchestrator, complete the following steps:

    1. Log in to the Cisco Discovery Orchestrator web interface.
    2. From the Cisco Discovery Orchestrator Policies menu, choose FTD Policies.
    3. From the FTD Policies menu, choose Access Control.
    4. Choose the appropriate Access Control Policy.
    5. Click the Edit pencil icon.
    6. Look in the Decryption area.
    7. If there is a policy name in the pop-up window, choose None from the drop-down menu and choose Apply.
    8. Choose Save.

    While these workarounds and mitigations have been deployed and were proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

**

Fixed Software

**

  • When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories page, to determine exposure and a complete upgrade solution.

    In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

    Cisco ASA, FMC, and FTD Software

    To help customers determine their exposure to vulnerabilities in Cisco ASA, FMC, and FTD Software, Cisco provides the Cisco Software Checker. This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities that are described in all the advisories that the Software Checker identifies (“Combined First Fixed”).

    To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to search for vulnerabilities that affect a specific software release. To use the form, follow these steps:

    1. Choose which advisories the tool will search-all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.
    2. Choose the appropriate software.
    3. Choose the appropriate platform.
    4. Enter a release number-for example, 9.16.2.11 for Cisco ASA Software or 6.6.7 for Cisco FTD Software.
    5. Click Check.

    For instructions on upgrading your FTD device, see Cisco Firepower Management Center Upgrade Guide.

**Additional Resources**

For help determining the best Cisco ASA, FTD, or FMC Software release, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

Cisco ASA Compatibility  
Cisco Secure Firewall ASA Upgrade Guide  
Cisco Secure Firewall Threat Defense Compatibility Guide

**

Exploitation and Public Announcements

**

  • The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

**

Source

**

  • This vulnerability was found during the resolution of a Cisco TAC support case.

**

Cisco Security Vulnerability Policy

**

  • To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
  • Subscribe

**

Related to This Advisory

**

  • Cisco Event Response: November 2023 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication

**

URL

**

  • https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sa-ftd-snort3-urldos-OccFQTeX

**

Revision History

**

  • Version

    Description

    Section

    Status

    Date

    1.0

    Initial public release.

    -

    Final

    2023-NOV-01

    Show Less

**

Legal Disclaimer

**

  • THIS DOCUMENT IS PROVIDED ON AN “AS IS” BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

    A standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products.

**

Feedback

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