CVE-2018-0311: Cisco Security Advisory: Cisco FXOS and NX-OS Software Cisco Fabric Services Denial of Service Vulnerability

Cisco Fabric Services provides a common infrastructure for distributing and synchronizing configuration data between Cisco devices that are on the same network and with virtual port channels (vPCs). This includes configuration data for applications and features that are compatible with and enabled to use Cisco Fabric Services-for example, Distributed Device Alias Services, Network Time Protocol (NTP), and user and administrator roles.

To distribute and synchronize data, Cisco Fabric Services can be configured to use any of the following distribution types:

• Cisco Fabric Services over Fibre Channel (CFSoFC)-Distributes data over a Fibre Channel (FC), such as a virtual storage area network (VSAN). CFSoFC distribution is enabled by default.
• Cisco Fabric Services over Ethernet (CFSoE)-Distributes data over an Ethernet network. For vPC support, Cisco Fabric Services must be configured to use this distribution type. CFSoE distribution is disabled by default.
• Cisco Fabric Services over IP (CFSoIP)-Distributes data over an IPv4 or IPv6 network. CFSoIP distribution is disabled by default.

The vulnerability described in this advisory is due to insufficient input validation that could occur when the affected software processes Cisco Fabric Services packets that it receives during distribution and synchronization operations. Exploitation of the vulnerability does not require any applications to be enabled to use Cisco Fabric Services. Instead, exploitation depends on which Cisco Fabric Services distribution types are configured for a device. In addition, the attack vectors vary based on which distribution types are configured, as follows:

• CFSoFC-An attack could occur via Fibre Channel over Ethernet (FCoE) or Fibre Channel over IP (FCIP), if FC ports are configured for a device. In this scenario, an attack could succeed in the data plane, not the management plane, of any FC port. If no FC ports are configured for a device, this distribution type cannot be used to exploit the vulnerability.
• CFSoE-An attack is possible from only a vPC peer or an attacker who has access to a vPC peer link. No other peer, neighbor, or network node can be used to exploit the vulnerability.
• CFSoIP-An attack is possible from any node that has IP network connectivity to the management interface of a device. In this scenario, an attack cannot succeed from the data plane.

If a device is enabled to use more than one distribution type, the applicable attack vectors for all those distribution types exist for the device.

Administrators can display configuration information and check the distribution status of Cisco Fabric Services for a device by using the show cfs status command in the device CLI, as shown in the following example:

switch# show cfs status
Distribution : Enabled Distribution over IP : Disabled IPv4 multicast address : 239.255.70.83 IPv6 multicast address : ff15::efff:4653 Distribution over Ethernet : Disabled

In the preceding example, the Enabled value in the Distribution field of the command output indicates that Cisco Fabric Services is enabled for the device and the device is configured to use the default Cisco Fabric Services distribution type, which is CFSoFC. The Disabled value in the Distribution over IP field and the Distribution over Ethernet field indicates that the device is not additionally configured to use the CFSoIP and CFSoE distribution types.

Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.

When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts 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.

Customers Without Service Contracts

Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.

Fixed Releases

Customers are advised to upgrade to an appropriate release as indicated in the applicable table in this section. To help ensure a complete upgrade solution, consider that this advisory is part of a collection. For a complete list of the advisories in the collection and links to them, see Cisco Event Response: June 2018 Cisco FXOS and NX-OS Software Security Advisory Collection.

In the following tables, the left column lists releases of Cisco FXOS or NX-OS Software. The center column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. The right column indicates whether a release is affected by all the vulnerabilities described in this collection of advisories and which release includes fixes for those vulnerabilities.

**Firepower 4100 Series Next-Generation Firewalls: **CSCve04859****

Cisco FXOS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

1.1

1.1.4.179

2.0.1.159

2.0

2.0.1.153

2.0.1.159

2.1.1

2.1.1.86

2.1.1.86 or 2.3.1.58

2.2.1

2.2.1.70

2.2.2.17 or 2.3.1.58

2.2.2

2.2.2.17

2.2.2.17 or 2.3.1.58

2.3

Not vulnerable

Not vulnerable

Firepower 9300 Security Appliance: CSCve04859

Cisco FXOS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

1.1

1.1.4.179

2.0.1.159

2.0

2.0.1.153

2.0.1.159

2.1.1

2.1.1.86

2.1.1.86 or 2.3.1.58

2.2.1

2.2.1.70

2.2.2.17 or 2.3.1.58

2.2.2

2.2.2.17

2.2.2.17 or 2.3.1.58

2.3

Not vulnerable

Not vulnerable

MDS 9000 Series Multilayer Switches: CSCvd69960

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

5.2

6.2(21)

8.1(1a) or 8.2(1)

6.2

6.2(21)

8.1(1a) or 8.2(1)

7.3

8.1(1a)

8.1(1a) or 8.2(1)

8.1

8.1(1a)

8.1(1a) or 8.2(1)

8.2

Not vulnerable

Not vulnerable

Nexus 3000 Series Switches: CSCve41537

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

Prior to 7.0(3)I4

7.0(3)I4(7)

7.0(3)I7(4)

7.0(3)I4

7.0(3)I4(7)

7.0(3)I7(4)

7.0(3)I5

7.0(3)I6(2)

7.0(3)I7(4)

7.0(3)I6

7.0(3)I6(2)

7.0(3)I7(4)

7.0(3)I7

Not vulnerable

7.0(3)I7(4)

Nexus 3500 Platform Switches: CSCve41530

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

6.0

6.0(2)A8(9)

7.0(3)I7(4)

7.0.3

Not vulnerable

7.0(3)I7(4)

Nexus 2000 Series Fabric Extenders and Nexus 5500, 5600, and 6000 Series Switches: CSCve02463

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

6.0

7.3(3)N1(1)

7.3(3)N1(1)

7.0

7.3(3)N1(1)

7.3(3)N1(1)

7.1

7.3(3)N1(1)

7.3(3)N1(1)

7.2

7.3(3)N1(1)

7.3(3)N1(1)

7.3

7.3(3)N1(1)

7.3(3)N1(1)

Nexus 7000 Series and 7700 Series Switches: CSCvd69960

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

6.2

6.2(20)

8.1(2) or 8.2(1)

7.2

7.3(2)D1(1)

8.1(2) or 8.2(1)

7.3

7.3(2)D1(1)

8.1(2) or 8.2(1)

8.0

8.1(2)

8.1(2) or 8.2(1)

8.1

8.1(2)

8.1(2) or 8.2(1)

8.2

Not vulnerable

Not vulnerable

Nexus 9000 Series Switches in standalone NX-OS mode: CSCve41537

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

Prior to 7.0(3)I4

7.0(3)I4(7)

7.0(3)I7(4)

7.0(3)I4

7.0(3)I4(7)

7.0(3)I7(4)

7.0(3)I5

7.0(3)I6(2)

7.0(3)I7(4)

7.0(3)I6

7.0(3)I6(2)

7.0(3)I7(4)

7.0(3)I7

Not vulnerable

7.0(3)I7(4)

Nexus 9500 R-Series Line Cards and Fabric Modules: CSCve41557

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

7.0

7.0(3)F3(1)

7.0(3)F3(3a)

**UCS 6100, 6200, and 6300 Series Fabric Interconnects: **CSCve41541****

Cisco NX-OS Software Release

First Fixed Release for This Vulnerability

First Fixed Release for All Vulnerabilities Described in the Collection of Advisories

Prior to 2.2

2.2(8m)

3.2(2b)

2.2

2.2(8m)

3.2(2b)

2.5

3.2(2b)

3.2(2b)

3.0

3.2(2b)

3.2(2b)

3.1

3.2(2b)

3.2(2b)

3.2

3.2(2b)

3.2(2b)