An Improper access control vulnerability in StBedtimeModeReceiver in Wear OS 3.0 prior to Firmware update Feb-2022 Release allows untrusted applications to change bedtime mode without a proper permission.

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CVE-2022-23994: Samsung Mobile Security

Improper input validation vulnerability in SmartTagPlugin prior to version 1.2.15-6 allows privileged attackers to trigger a XSS on a victim's devices.

CVE-2022-24926: Samsung Mobile Security

ismsEx service is a vendor service in unisoc equipment?ismsEx service is an extension of sms system service?but it does not check the permissions of the caller?resulting in permission leaks?Third-party apps can use this service to arbitrarily modify and set system properties?Product: AndroidVersions: Android SoCAndroid ID: A-207479207

_Published February 7, 2022 | Updated February 17, 2022_

The Android Security Bulletin contains details of security vulnerabilities affecting Android devices. Security patch levels of 2022-02-05 or later address all of these issues. To learn how to check a device's security patch level, see Check and update your Android version.

Android partners are notified of all issues at least a month before publication. Source code patches for these issues have been released to the Android Open Source Project (AOSP) repository and linked from this bulletin. This bulletin also includes links to patches outside of AOSP

The most severe of these issues is a critical security vulnerability in the System component that could lead to remote escalation of privilege with no additional execution privileges needed. The severity assessment is based on the effect that exploiting the vulnerability would possibly have on an affected device, assuming the platform and service mitigations are turned off for development purposes or if successfully bypassed.

Refer to the Android and Google Play Protect mitigations section for details on the Android security platform protections and Google Play Protect, which improve the security of the Android platform.

**Android and Google service mitigations**

This is a summary of the mitigations provided by the Android security platform and service protections such as Google Play Protect. These capabilities reduce the likelihood that security vulnerabilities could be successfully exploited on Android.

*   Exploitation for many issues on Android is made more difficult by enhancements in newer versions of the Android platform. We encourage all users to update to the latest version of Android where possible.
*   The Android security team actively monitors for abuse through Google Play Protect and warns users about Potentially Harmful Applications. Google Play Protect is enabled by default on devices with Google Mobile Services, and is especially important for users who install apps from outside of Google Play.

**2022-02-01 security patch level vulnerability details**

In the sections below, we provide details for each of the security vulnerabilities that apply to the 2022-02-01 patch level. Vulnerabilities are grouped under the component they affect. Issues are described in the tables below and include CVE ID, associated references, type of vulnerability, severity, and updated AOSP versions (where applicable). When available, we link the public change that addressed the issue to the bug ID, like the AOSP change list. When multiple changes relate to a single bug, additional references are linked to numbers following the bug ID. Devices with Android 10 and later may receive security updates as well as Google Play system updates.

**Framework**

The most severe vulnerability in this section could lead to local escalation of privilege with no additional execution privileges needed.

    

CVE

References

Type

Severity

Updated AOSP versions

CVE-2021-39619

A-197399948

EoP

High

11, 12

CVE-2021-39663

A-200682135\*

EoP

High

10

CVE-2021-39676

A-197228210\*

EoP

High

11

CVE-2021-39664

A-203938029

ID

High

12

**Media Framework**

The most severe vulnerability in this section could lead to local escalation of privilege with no additional execution privileges needed.

    

CVE

References

Type

Severity

Updated AOSP versions

CVE-2020-13112

A-194342672\*

EoP

High

10, 11

CVE-2020-13113

A-196085005\*

EoP

High

10, 11

CVE-2021-39665

A-204077881

ID

High

12

CVE-2021-39666

A-204445255 \[2\]

ID

High

11, 12

**System**

The most severe vulnerability in this section could lead to remote escalation of privilege with no additional execution privileges needed.

    

CVE

References

Type

Severity

Updated AOSP versions

CVE-2021-39675

A-205729183

EoP

Critical

12

CVE-2021-39668

A-193445603

EoP

High

11, 12

CVE-2021-39669

A-196969991

EoP

High

11, 12

CVE-2021-39671

A-206718630 \[2\]

EoP

High

12

CVE-2021-39674

A-201083442

EoP

High

10, 11, 12

CVE-2021-0706

A-193444889\*

DoS

High

10, 11

**2022-02-05 security patch level vulnerability details**

In the sections below, we provide details for each of the security vulnerabilities that apply to the 2022-02-05 patch level. Vulnerabilities are grouped under the component they affect. Issues are described in the tables below and include CVE ID, associated references, type of vulnerability, severity, and updated AOSP versions (where applicable). When available, we link the public change that addressed the issue to the bug ID, like the AOSP change list. When multiple changes relate to a single bug, additional references are linked to numbers following the bug ID.

**System**

The vulnerability in this section could lead to local information disclosure with no additional execution privileges needed.

    

CVE

References

Type

Severity

Updated AOSP versions

CVE-2021-39631

A-193890833 \[2\]

ID

High

10, 11, 12

**Amlogic components**

This vulnerability affects Amlogic components and further details are available directly from Amlogic. The severity assessment of this issue is provided directly by Amlogic.

   

CVE

References

Severity

Component

CVE-2021-39672  

A-202018701\*

High

Fastboot

**MediaTek components**

These vulnerabilities affect MediaTek components and further details are available directly from MediaTek. The severity assessment of these issues is provided directly by MediaTek.

   

CVE

References

Severity

Component

CVE-2022-20024  

A-209705228  
M-ALPS06219064\*

High

System service

CVE-2022-20025

A-209700749  
M-ALPS06126832\*

High

Bluetooth

CVE-2022-20026

A-209705229  
M-ALPS06126827\*

High

Bluetooth

CVE-2022-20027

A-209702508  
M-ALPS06126826\*

High

Bluetooth

CVE-2022-20028

A-209702509  
M-ALPS06198663\*

High

Bluetooth

**Unisoc components**

These vulnerabilities affect Unisoc components and further details are available directly from Unisoc. The severity assessment of these issues is provided directly by Unisoc.

   

CVE

References

Severity

Component

CVE-2021-39616

A-204686438  
U-1704529\*

High

sprd-vowifi

CVE-2021-39635

A-206492634  
U-1731024\*

High

ims\_ex

CVE-2021-39658

A-207479207  
U-1732729\*

High

IsmsEx

**Qualcomm components**

These vulnerabilities affect Qualcomm components and are described in further detail in the appropriate Qualcomm security bulletin or security alert. The severity assessment of these issues is provided directly by Qualcomm.

   

CVE

References

Severity

Component

CVE-2021-35068  

A-202025798  
QC-CR#2982971

High

Bluetooth

CVE-2021-35069  

A-203032261  
QC-CR#3001191

High

WLAN

CVE-2021-35074

A-204905255  
QC-CR#2998013

High

Kernel

CVE-2021-35075  

A-204905325  
QC-CR#2998149

High

Kernel

CVE-2021-35077

A-204904989  
QC-CR#3007135

High

Kernel

**Qualcomm closed-source components**

These vulnerabilities affect Qualcomm closed-source components and are described in further detail in the appropriate Qualcomm security bulletin or security alert. The severity assessment of these issues is provided directly by Qualcomm.

   

CVE

References

Severity

Component

CVE-2021-30317

A-195750667\*

Critical

Closed-source component

CVE-2021-30309

A-195750718\*

High

Closed-source component

CVE-2021-30318

A-202025316\*

High

Closed-source component

CVE-2021-30322

A-195751178\*

High

Closed-source component

CVE-2021-30323

A-195750446\*

High

Closed-source component

CVE-2021-30326

A-195751080\*

High

Closed-source component

**Common questions and answers**

This section answers common questions that may occur after reading this bulletin.

**1\. How do I determine if my device is updated to address these issues?**

To learn how to check a device's security patch level, see Check and update your Android version.

*   Security patch levels of 2022-02-01 or later address all issues associated with the 2022-02-01 security patch level.
*   Security patch levels of 2022-02-05 or later address all issues associated with the 2022-02-05 security patch level and all previous patch levels.

Device manufacturers that include these updates should set the patch string level to:

*   \[ro.build.version.security\_patch\]:\[2022-02-01\]
*   \[ro.build.version.security\_patch\]:\[2022-02-05\]

For some devices on Android 10 or later, the Google Play system update will have a date string that matches the 2022-02-01 security patch level. Please see this article for more details on how to install security updates.

**2\. Why does this bulletin have two security patch levels?**

This bulletin has two security patch levels so that Android partners have the flexibility to fix a subset of vulnerabilities that are similar across all Android devices more quickly. Android partners are encouraged to fix all issues in this bulletin and use the latest security patch level.

*   Devices that use the 2022-02-01 security patch level must include all issues associated with that security patch level, as well as fixes for all issues reported in previous security bulletins.
*   Devices that use the security patch level of 2022-02-05 or newer must include all applicable patches in this (and previous) security bulletins.

Partners are encouraged to bundle the fixes for all issues they are addressing in a single update.

**3\. What do the entries in the _Type_ column mean?**

Entries in the _Type_ column of the vulnerability details table reference the classification of the security vulnerability.

 

Abbreviation

Definition

RCE

Remote code execution

EoP

Elevation of privilege

ID

Information disclosure

DoS

Denial of service

N/A

Classification not available

**4\. What do the entries in the _References_ column mean?**

Entries under the _References_ column of the vulnerability details table may contain a prefix identifying the organization to which the reference value belongs.

 

Prefix

Reference

A-

Android bug ID

QC-

Qualcomm reference number

M-

MediaTek reference number

N-

NVIDIA reference number

B-

Broadcom reference number

U-

UNISOC reference number

**5\. What does an \* next to the Android bug ID in the _References_ column mean?**

Issues that are not publicly available have an \* next to the corresponding reference ID. The update for that issue is generally contained in the latest binary drivers for Pixel devices available from the Google Developer site.

**6\. Why are security vulnerabilities split between this bulletin and device / partner security bulletins, such as the Pixel bulletin?**

Security vulnerabilities that are documented in this security bulletin are required to declare the latest security patch level on Android devices. Additional security vulnerabilities that are documented in the device / partner security bulletins are not required for declaring a security patch level. Android device and chipset manufacturers may also publish security vulnerability details specific to their products, such as Google, Huawei, LGE, Motorola, Nokia, or Samsung.

**Versions**

  

Version

Date

Notes

1.0

February 7, 2022

Bulletin Released

1.1

February 8, 2022

Bulletin revised to include AOSP links

1.2

February 17, 2022

Revised CVE table

CVE-2021-39658: Android Security Bulletin—February 2022  |  Android Open Source Project

Improper authorization in TelephonyManager prior to SMR Jan-2022 Release 1 allows attackers to get IMSI without READ_PRIVILEGED_PHONE_STATE permission

CVE-2022-22272: Samsung Mobile Security

Improper authorization vulnerability in Galaxy Store prior to 4.5.36.5 allows remote app installation of the allowlist.

CVE-2022-22288: Samsung Mobile Security

In createFromParcel of OutputConfiguration.java, there is a possible parcel serialization/deserialization mismatch due to improper input validation. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-10 Android-11 Android-9Android ID: A-188675581

_Published November 1, 2021 | Updated December 3, 2021_

The Android Security Bulletin contains details of security vulnerabilities affecting Android devices. Security patch levels of 2021-11-06 or later address all of these issues. To learn how to check a device's security patch level, see Check and update your Android version.

Android partners are notified of all issues at least a month before publication. Source code patches for these issues have been released to the Android Open Source Project (AOSP) repository and linked from this bulletin. This bulletin also includes links to patches outside of AOSP

The most severe of these issues is a critical security vulnerability in the System component that could enable a remote attacker using a specially crafted transmission to execute arbitrary code within the context of a privileged process. The severity assessment is based on the effect that exploiting the vulnerability would possibly have on an affected device, assuming the platform and service mitigations are turned off for development purposes or if successfully bypassed.

Refer to the Android and Google Play Protect mitigations section for details on the Android security platform protections and Google Play Protect, which improve the security of the Android platform.

**Android and Google service mitigations**

This is a summary of the mitigations provided by the Android security platform and service protections such as Google Play Protect. These capabilities reduce the likelihood that security vulnerabilities could be successfully exploited on Android.

*   Exploitation for many issues on Android is made more difficult by enhancements in newer versions of the Android platform. We encourage all users to update to the latest version of Android where possible.
*   The Android security team actively monitors for abuse through Google Play Protect and warns users about Potentially Harmful Applications. Google Play Protect is enabled by default on devices with Google Mobile Services, and is especially important for users who install apps from outside of Google Play.

**2021-11-01 security patch level vulnerability details**

In the sections below, we provide details for each of the security vulnerabilities that apply to the 2021-11-01 patch level. Vulnerabilities are grouped under the component they affect. Issues are described in the tables below and include CVE ID, associated references, type of vulnerability, severity, and updated AOSP versions (where applicable). When available, we link the public change that addressed the issue to the bug ID, like the AOSP change list. When multiple changes relate to a single bug, additional references are linked to numbers following the bug ID. Devices with Android 10 and later may receive security updates as well as Google Play system updates.

**Framework**

The most severe vulnerability in this section could enable a local attacker to gain access to additional permissions with no user interaction required.

    

CVE

References

Type

Severity

Updated AOSP versions

CVE-2021-0799

A-197647956

EoP

High

12

CVE-2021-0921

A-195962697

EoP

High

11

CVE-2021-0923

A-195338390

EoP

High

12

CVE-2021-0926

A-191053931

EoP

High

9, 10, 11, 12

CVE-2021-0933

A-172251622

EoP

High

9, 10, 11, 12

CVE-2020-13871

A-192606047

ID

High

11

CVE-2021-0653

A-177931370

ID

High

9, 10, 11

CVE-2021-0922

A-195630721

EoP

Moderate

11

**Media Framework**

The most severe vulnerability in this section could enable a local malicious application to bypass user interaction requirements in order to gain access to additional permissions.

    

CVE

References

Type

Severity

Updated AOSP versions

CVE-2021-0928

A-188675581

EoP

High

9, 10, 11

CVE-2021-0650

A-190286685

ID

High

9, 10, 11

**System**

The most severe vulnerability in this section could enable a remote attacker using a specially crafted transmission to execute arbitrary code within the context of a privileged process.

    

CVE

References

Type

Severity

Updated AOSP versions

CVE-2021-0918

A-197536150

RCE

Critical

12

CVE-2021-0930

A-181660091

RCE

Critical

9, 10, 11, 12

CVE-2021-0434

A-167403112 \[2\] \[3\] \[4\] \[5\] \[6\]

EoP

High

9, 10, 11

CVE-2021-0649

A-191382886 \[2\]

EoP

High

11

CVE-2021-0932

A-173025705

EoP

High

10

CVE-2021-0925

A-191444150

ID

High

12

CVE-2021-0931

A-180747689

ID

High

9, 10, 11, 12

CVE-2021-0919

A-197336441

DoS

Moderate

9, 10, 11

**Google Play system updates**

The following issues are included in Project Mainline components.

 

Component

CVE

Tethering

CVE-2021-0653

Media Framework components

CVE-2021-0650

Tethering

CVE-2021-0649

**2021-11-05 security patch level vulnerability details**

In the sections below, we provide details for each of the security vulnerabilities that apply to the 2021-11-05 patch level. Vulnerabilities are grouped under the component they affect. Issues are described in the tables below and include CVE ID, associated references, type of vulnerability, severity, and updated AOSP versions (where applicable). When available, we link the public change that addressed the issue to the bug ID, like the AOSP change list. When multiple changes relate to a single bug, additional references are linked to numbers following the bug ID.

**Kernel components**

The most severe vulnerability in this section could result in local escalation of privilege due to a use after free.

    

CVE

References

Type

Severity

Component

CVE-2021-0920

A-196926917  
Upstream kernel

EoP

High

Kernel

CVE-2021-0924

A-194461020  
Upstream kernel

EoP

High

USB

CVE-2021-0929

A-187527909  
Upstream kernel \[2\] \[3\]

EoP

High

ION

**Android TV**

The most severe vulnerability in this section could enable a proximate attacker to silently pair with a TV and execute arbitrary code with no privileges or user interaction required.

    

CVE

References

Type

Severity

Component

CVE-2021-0889

A-180745296

RCE

Critical

Android TV Remote Service

CVE-2021-0927

A-189824175

EoP

High

TvInputManager

**MediaTek components**

This vulnerability affects MediaTek components and further details are available directly from MediaTek. The severity assessment of this issue is provided directly by MediaTek.

    

CVE

References

Severity

Component

CVE-2021-0672  

A-199678035  
M-ALPS05969704 \*

High

Browser app

**Qualcomm closed-source components**

These vulnerabilities affect Qualcomm closed-source components and are described in further detail in the appropriate Qualcomm security bulletin or security alert. The severity assessment of these issues is provided directly by Qualcomm.

    

CVE

References

Severity

Component

CVE-2021-1924  

A-187074639 \*

Critical

Closed-source component

CVE-2021-1975  

A-187074053 \*

Critical

Closed-source component

CVE-2021-1921  

A-187074562 \*

High

Closed-source component

CVE-2021-1973  

A-187074563 \*

High

Closed-source component

CVE-2021-1979  

A-187073200 \*

High

Closed-source component

CVE-2021-1981  

A-187074764 \*

High

Closed-source component

CVE-2021-1982  

A-187074484 \*

High

Closed-source component

CVE-2021-30254  

A-187074014 \*

High

Closed-source component

CVE-2021-30255  

A-187074054 \*

High

Closed-source component

CVE-2021-30284  

A-187074013 \*

High

Closed-source component

**2021-11-06 security patch level vulnerability details**

In the sections below, we provide details for each of the security vulnerabilities that apply to the 2021-11-06 patch level. Vulnerabilities are grouped under the component they affect. Issues are described in the tables below and include CVE ID, associated references, type of vulnerability, severity, and updated AOSP versions (where applicable). When available, we link the public change that addressed the issue to the bug ID, like the AOSP change list. When multiple changes relate to a single bug, additional references are linked to numbers following the bug ID.

**Kernel components**

The vulnerability in this section could lead to a local escalation of privilege due to a use after free.

    

CVE

References

Type

Severity

Component

CVE-2021-1048

A-204573007  
Upstream kernel

EoP

High

Kernel

**Common questions and answers**

This section answers common questions that may occur after reading this bulletin.

**1\. How do I determine if my device is updated to address these issues?**

To learn how to check a device's security patch level, see Check and update your Android version.

*   Security patch levels of 2021-11-01 or later address all issues associated with the 2021-11-01 security patch level.
*   Security patch levels of 2021-11-05 or later address all issues associated with the 2021-11-05 security patch level and all previous patch levels.
*   Security patch levels of 2021-11-06 or later address all issues associated with the 2021-11-06 security patch level and all previous patch levels.

Device manufacturers that include these updates should set the patch string level to:

*   \[ro.build.version.security\_patch\]:\[2021-11-01\]
*   \[ro.build.version.security\_patch\]:\[2021-11-05\]
*   \[ro.build.version.security\_patch\]:\[2021-11-06\]

For some devices on Android 10 or later, the Google Play system update will have a date string that matches the 2021-11-01 security patch level. Please see this article for more details on how to install security updates.

**2\. Why does this bulletin have two security patch levels?**

This bulletin has two security patch levels so that Android partners have the flexibility to fix a subset of vulnerabilities that are similar across all Android devices more quickly. Android partners are encouraged to fix all issues in this bulletin and use the latest security patch level.

*   Devices that use the 2021-11-01 security patch level must include all issues associated with that security patch level, as well as fixes for all issues reported in previous security bulletins.
*   Devices that use the security patch level of 2021-11-05 or newer must include all applicable patches in this (and previous) security bulletins.
*   Devices that use the security patch level of 2021-11-06 or newer must include all applicable patches in this (and previous) security bulletins.

Partners are encouraged to bundle the fixes for all issues they are addressing in a single update.

**3\. What do the entries in the _Type_ column mean?**

Entries in the _Type_ column of the vulnerability details table reference the classification of the security vulnerability.

 

Abbreviation

Definition

RCE

Remote code execution

EoP

Elevation of privilege

ID

Information disclosure

DoS

Denial of service

N/A

Classification not available

**4\. What do the entries in the _References_ column mean?**

Entries under the _References_ column of the vulnerability details table may contain a prefix identifying the organization to which the reference value belongs.

 

Prefix

Reference

A-

Android bug ID

QC-

Qualcomm reference number

M-

MediaTek reference number

N-

NVIDIA reference number

B-

Broadcom reference number

U-

UNISOC reference number

**5\. What does an \* next to the Android bug ID in the _References_ column mean?**

Issues that are not publicly available have an \* next to the corresponding reference ID. The update for that issue is generally contained in the latest binary drivers for Pixel devices available from the Google Developer site.

**6\. Why are security vulnerabilities split between this bulletin and device / partner security bulletins, such as the Pixel bulletin?**

Security vulnerabilities that are documented in this security bulletin are required to declare the latest security patch level on Android devices. Additional security vulnerabilities that are documented in the device / partner security bulletins are not required for declaring a security patch level. Android device and chipset manufacturers may also publish security vulnerability details specific to their products, such as Google, Huawei, LGE, Motorola, Nokia, or Samsung.

**Versions**

  

Version

Date

Notes

1.0

November 1, 2021

Bulletin Released

1.1

November 2, 2021

Bulletin revised to include AOSP links

1.2

December 3, 2021

Revised CVE table

CVE-2021-0928: Android Security Bulletin—November 2021

Intent redirection vulnerability in Samsung Blockchain Wallet prior to version 1.3.02.8 allows attacker to execute privileged action.

CVE-2021-25526

Improper authorization vulnerability in Samsung Flow mobile application prior to 4.8.03.5 allows Samsung Flow PC application connected with user device to access part of notification data in Secure Folder without authorization.

CVE-2021-25507

check_smart before 6.9.1 allows unintended drive access by an unprivileged user because it only checks for a substring match of a device path (the /dev/bus substring and a number), aka an unanchored regular expression.

CVE-2021-42257: monitoring nagios plugin check_smart SMART Hard Drive Solid State Drive NVMe Check

Fetchmail before 6.4.22 fails to enforce STARTTLS session encryption in some circumstances, such as a certain situation with IMAP and PREAUTH.

**Why TLS is better without STARTTLS  
A Security Analysis of STARTTLS in the Email Context**

by Damian Poddebniak¹, Fabian Ising¹, Hanno Böck², and Sebastian Schinzel¹

¹ Münster University of Applied Sciences ² Independent Researcher

_Full paper published at USENIX Security 21_

**Introduction**

Connections between email clients and servers provide two ways to be protected with TLS: While implicit TLS encrypts the connection from the start and runs on a separate port, STARTTLS provides a mechanism to upgrade existing unencrypted connections to TLS.

Sometimes STARTTLS is seen as an opportunistic encryption mode that provides TLS protection only when available. This is trivially vulnerable to downgrade attacks. However, modern email clients usually have the expectation that STARTTLS is enforced, and when enabled, no unencrypted communication is possible.

Upgrading connections via STARTTLS is fragile and vulnerable to a number of security vulnerabilities and attacks. We found more than 40 vulnerabilities in STARTTLS implementations. We conclude that these vulnerabilities are so common that we recommend to avoid using STARTTLS when possible.

**Attacks**

We assume a Meddler-in-the-Middle (MitM) attacker who can modify connections established between an email client and the email server of an provider.

**Stealing Login Credentials with SMTP and IMAP via Command Injection**

In 2011 Postfix developer Wietse Venema described a bug in STARTTLS implementations that allowed injecting plaintext commands that a server interprets as if they were part of the encrypted connection. This works by sending additional commands with the STARTTLS command to the server in the same TCP segment.

We found that despite being known since 2011, this vulnerability is still very common. We found 15 vulnerable implementations, and in scans, 2% of all mail servers showed this vulnerability.

This command injection can be used to steal credentials with the SMTP and IMAP protocols.

Our attack requires a Meddler in the Middle (MitM) attacker that can modify network traffic and has login credentials for their own account on the same server. The attacker can inject commands that authenticate them and then start sending (SMTP) or storing (IMAP) an email. The login credentials sent by the victim will be stored in the email that the attacker can access.

The command injection can also be used for a cross-protocol attack to serve HTTPS content with the mail server's certificate. Detailed descriptions of these attacks can be found in our paper.

**Mailbox content forgery via Response Injection**

We discovered an attack similar to the command injection in email client applications. We call this a response injection. This bug affected many popular mail clients, including Apple Mail, Mozilla Thunderbird, Claws Mail, and Mutt.

By injecting additional content to the server message in response to the STARTTLS command before the TLS handshake, we can inject server commands that the client will process as if they were part of the encrypted connection. This can be used to forge mailbox content.

**IMAP connection downgrade via PREAUTH and credential-stealing with REFERRAL**

In the IMAP protocol, a server can signal the client in the first message that it is already authenticated via the PREAUTH command. The protocol forbids using the STARTTLS command in an authenticated state. Therefore if a client application accepts PREAUTH, it cannot enforce STARTTLS.

A Meddler in the Middle attacker can use this to prevent STARTTLS from upgrading the connection and force a client to an unencrypted connection.

This vulnerability was originally found in Trojitá in 2014. We discovered that multiple other email client applications were vulnerable to the same bug.

This bug is especially severe in combination with the IMAP features Login Referrals and Mailbox Referrals. These commands allow a server to instruct a client to log into another IMAP server. By using PREAUTH to prevent an encrypted connection, an attacker can use referrals to force a client to send credentials to an attacker-controlled server. Fortunately, the referral features are not supported by many clients. We found only one client - Alpine - vulnerable to this combination of PREAUTH and referrals.

**Additional Attacks**

We found additional attacks, whose security impact may vary for implementations. Please see our paper to learn more about these attacks.

**Conclusion**

All vulnerabilities described here rely on the transition of an insecure connection to a secure connection. Implicit TLS does not have such a transition and is therefore not vulnerable to any of these attacks. We therefore consider implicit TLS a more secure option than STARTTLS.

We also point out that STARTTLS always introduces at least one extra connection round trip. So implicit TLS generally provides better performance.

**Impact**

The demonstrated attacks require an active attacker and may be recognized when used against an email client that tries to enforce the transition to TLS. We have informed all popular email client and server vendors and most issues are already fixed. We think that the demonstrated attacks would be difficult to execute on a large scale and we primarily expect them to be used in targeted attacks. As a general recommendation you should always update your software and (to also profit from faster connections) reconfigure your email client to use implicit TLS only (see below).

**Recommendations****For Email Client Users**

If possible, we recommend that users check and configure their email clients to use SMTP, POP3 and IMAP with implicit TLS on dedicated ports, i.e., SMTP/Submission on port 465, POP3 on port 995, and IMAP on port 993. This is in line with already existing recommendations in RFC 8314 and was already recommended by security professionals before.

Some mail service providers, notably Microsoft and Apple, do not support implicit TLS for SMTP/Submission. We recommend that users ask their mail service providers to offer the more secure implicit TLS option.

**For Application Developers**

Both email server and client applications should offer implicit TLS by default. In the long term software developers may decide to not support STARTTLS at all and thus simplify both their code and configuration dialogs and files.

We recommend auditing all applications supporting STARTTLS - both on the server and the client side - for the bugs discovered. Most importantly, applications need to ensure that no unencrypted content gets processed as part of an encrypted connection. IMAP applications must make sure that they do not allow PREAUTH in combination with STARTTLS. We provide the EAST toolkit, which allows testing applications.

**For Mail Server Administrators**

Make sure your server supports implicit TLS for all supported protocols. If possible, consider disabling STARTTLS for IMAP, POP3 and SMTP submission.

If you really need to support STARTTLS, we recommend testing your server with our tool for the command injection vulnerability for all supported protocols. If your server software is vulnerable, you should ask your vendor for a security update.

**FAQ****Isn't STARTTLS insecure anyway?**

STARTTLS is used in two "modes", "opportunistic", and "enforced". Email clients must authenticate themselves with a username and password before submitting a new email or accessing existing emails. For these connections, the transition to TLS via STARTTLS **must** be strictly enforced because a downgrade would reveal the username and password and give an attacker full access to the email account.

**How can I test if my software is vulnerable?**

We provide the EAST toolkit that allows testing email clients and servers.

**Testing an email server** for the command injection is relatively easy with our Command Injection Tester. testssl.sh (dev version) and TLS-Attacker/TLS-Scanner (starttls branch) also check for the command injection.

**Testing an email client** is more complex, and we refer to EAST's Fake Mail Server component.

**Are other protocols with support for STARTTLS or similar mechanisms affected?**

We expect to see similar vulnerabilities in other protocols using STARTTLS, e.g., XMPP, FTP, IRC, or LDAP. Thus our recommendation to avoid STARTTLS and use implicit TLS when possible applies to those protocols as well. We encourage security researchers to look for such vulnerabilities in other protocols.

Some protocols only support STARTTLS and provide no implicit TLS mechanism. We recommend that standards bodies define implicit TLS modes for these protocols and that future protocols do this by default and avoid STARTTLS completely.

**What about communication between email servers (MTA to MTA)?**

Traditionally, STARTTLS between email servers only protects against passive attacks and is vulnerable to active attacks such as STARTTLS stripping. Thus STARTTLS vulnerabilities do not give an advantage to the attacker.

However, efforts like MTA-STS and DANE provide authentication mechanisms for MTA to MTA connections. Therefore server software should be investigated for STARTTLS vulnerabilities as well. Particularly relevant are the buffering bugs, which can happen both for the sending (response injection) and receiving (command injection) side of a mail server. We have found and reported some vulnerabilities in server software during our research.

Currently, there is no standardized way to use implicit TLS for MTA to MTA connections. Therefore, it is not possible to avoid STARTTLS without changes to the protocol specification.

**How important is this?**

It's not the most important thing you should worry about today.

**How can I contact you?**

You can reach us via mail or twitter:

*   Damian Poddebniak, @dues\_\_, poddebniak@fh-muenster.de
*   Fabian Ising, @Murgi, F.Ising@fh-muenster.de
*   Hanno Böck, @hanno, hanno@hboeck.de
*   Sebastian Schinzel, @seecurity, schinzel@fh-muenster.de

**Reported Vulnerabilities**

The following is a list of all STARTTLS-related vulnerabilities we found during our research. None of the issues would be present if implicit TLS would have been used exclusively. Due to different kinds of reports, not all issues are publicly documented. All issues were reported more than than 90 days ago.

**Email Clients**

As an end user, make sure to use the newest version of your email software. The following list serves as a quick check if your client is still affected.

**Response Injection (Buffering)**

Product

Protocol

Status

Links

Apple Mail (macOS)

SMTP/POP3/IMAP

Fixed in macOS High Sierra 10.13.6/Big Sur 11.4

CVE-2020-9941, CVE-2021-30696

Apple Mail (iOS/iPadOS)

SMTP/POP3/IMAP

Fixed in iOS/iPadOS 14.0

CVE-2020-9941

Mozilla Thunderbird

IMAP

Fixed in 78.7.0

CVE-2020-15685, Vendor advisory, Bug report

Claws Mail

SMTP/POP3/IMAP

Fixed in 3.17.6 for SMTP/POP3, See libEtPan for IMAP

CVE-2020-15917

Mutt

IMAP/SMTP/POP3

Fixed in 1.14.4

CVE-2020-14954

NeoMutt

IMAP/SMPT/POP3

Fixed in 2020-06-19

Commit/Patch, see also CVE-2020-14954

Evolution

SMTP/POP3

Fixed in 3.36.4 (evolution-data-server)

CVE-2020-14928

LibEtPan (Mail Framework for C Language)

IMAP/SMTP/POP3

Fixed in repository, unreleased

CVE-2020-15953

Exim (MTA sending)

SMTP

Unfixed (reported privately)

CVE-2021-38371

Gmail (iOS/iPadOS)

SMTP/IMAP

Unfixed (reported privately)

\-

Mail.ru, MyMail

SMTP

Unfixed (reported privately, report closed as not applicable)

\-

Yandex

SMTP/IMAP

Unfixed (reported privately)

\-

PHP (stream\_socket\_enable\_crypto)

SMTP/POP3/IMAP

Unfixed

Bug report (private)

**Negotiation and Tampering bugs**

Product

Description

Protocol

Status

Links

Gmail (Android)

Leak of emails

IMAP

Fixed (retested in 2021.07.11.387440246)

\-

Gmail (Go)

Leak of emails

IMAP

Fixed (retested in 2020.10.15.341102866)

\-

Samsung Email

Leak of emails

IMAP

Fixed (untested)

\-

Alpine

Untagged responses accepted before STARTTLS

IMAP

Unknown (reported via email)

\-

Trojitá Trojita

Untagged responses accepted before STARTTLS

IMAP

Unknown

Bug report

Mozilla Thunderbird

Server responses prior to STARTTLS processed

IMAP

Fixed in 78.12

CVE-2021-29969, Vendor advisory

KMail

STARTTLS ignored when "Server requires authentication" not checked

SMTP

Unfixed

Bug report

Sylpheed

STARTTLS stripping

IMAP

Unknown

Bug report

OfflineIMAP

STARTTLS stripping

IMAP

Unknown

Bug report

GMX / Web.de Mail Collector

STARTTLS stripping

POP3/IMAP

Fixed

\-

Mail.ru, MyMail, Email app for Gmail

STARTTLS Stripping

SMTP

Unfixed (report closed as not applicable)

\-

**Avoiding Encryption via IMAP PREAUTH**

Product

Status

Links

Apple Mail (iOS/iPadOS)

Fixed in iOS 15.1

\-

Mozilla Thunderbird

Fixed in 68.9.0

CVE-2020-12398

Alpine

Fixed in 2.23

CVE-2020-14929, Commit

Mutt

Fixed in 1.14.3

CVE-2020-14093

NeoMutt

Fixed in Release 2020-06-19

Commit/Patch, see also CVE-2020-14093

GMX / Web.de Mail Collector

Fixed

\-

**Certificate Validation**

Product

Protocol

Description

Status

Links

OfflineIMAP

IMAP

Accepts untrusted certificates

Unknown

Bug report

GMX / Web.de Mail Collector

POP3/IMAP

Accepts untrusted certificates

Still allows self-signed

\-

Yandex

SMTP/IMAP

Accepts untrusted certificates

Unknown (report closed as not eligible)

\-

Mail.ru, MyMail

SMTP

Accepts untrusted certificates (SMTP, IMAP)

Unknown (report closed as duplicate)

\-

Outlook (Android & iOS)

SMTP/IMAP

Certificate hostname not checked (SMTP, IMAP)

Unknown (report closed as low/medium severity)

\-

Geary

SMTP/IMAP

Accepting an untrusted certificate creates a permanent trust exception for all certificates

Fixed in 3.36.3

CVE-2020-24661

Trojitá Trojita

SMTP

Accepts untrusted certificates

Fixed in repository (77ddd5d4) (no official releases)

CVE-2020-15047

Ruby Net::SMTP

SMTP

Only checks hostname, ignores certificate signature

Fixed in 2.7.2

Bug report

**Crashes**

Product

Protocol

Description

Status

Links

Alpine

IMAP

Crash when LIST or LSUB send before STARTTLS

Unknown (reported via email)

\-

Balsa

IMAP

Nullptr dereference when TLS required and PREAUTH send

Fixed in 2.5.10

CVE-2020-16118

Balsa

IMAP

Stack overflow due to repeated BAD answer to CAPABILITY command

Fixed in 2.6.3

Bug Report

Balsa

IMAP

Crash on untagged EXPUNGE response

Fixed in 2.6.3

Bug Report

Evolution

IMAP

Invalid free when no auth mechanisms in greeting

Fixed in >3.35.91

CVE-2020-16117

**Miscellaneous**

Product

Protocol

Description

Status

Links

KMail

POP3

Setup wizard in POP3 defaults to unencrypted connections

Unfixed

Bug Report

KMail

POP3

Config shows "encrypted", but it isn't

Unfixed

CVE-2020-15954

KMail

SMTP/IMAP

Dialog loop "forces" the user to accept invalid certificates

Unfixed

Bug Report

Mozilla Thunderbird

POP3

Infinite loop when POP3 server replies with -ERR to STLS command

Unknown

Bug Report

Trojitá Trojita

SMTP/IMAP

Hard to choose implicit TLS due to typo (German)

Fixed

Bug Report

Trojitá Trojita

SMTP

SMTP defaults to plaintext on port 587

Unknown

Bug Report

**Email Servers**

We found 320.000 vulnerable email servers in an Internet-wide scan and conducted a coordinated disclosure involving different CERTs. It is impracticable to inform and keep track of the update process of all mail service providers on the Internet, and thus we identified and prioritized popular mail service providers. We only list these in the following table.

Server issues are generally more severe than client issues. Unfortunately, no client configuration prevents server issues from being exploited, not even the usage of implicit TLS. Thus, you must ensure that your server (or your mail service provider) is not affected by STARTTLS issues.

You can use our command\_injection\_tester tool to verify that your server is not affected by the most severe issue.

**Command Injection (Buffering)**

Product

Protocol

Status

Links

Nemesis (used by GMX / Web.de, provider)

POP3/IMAP

Fixed (reported privately)

\-

Interia.pl (provider)

SMTP/POP3/IMAP

Fixed (reported privately)

\-

Yahoo (only MTA-to-MTA, provider)

SMTP

Unfixed (reported privately)

\-

Yandex (provider)

SMTP/POP3/IMAP

Unfixed (reported privately)

\-

s/qmail

SMTP

Fixed in 4.0.09

CVE-2020-15955

Coremail

SMTP/POP3/IMAP

Unfixed (reported via CERT)

\-

Citadel

SMTP/POP3/IMAP

Unfixed

CVE-2020-29547, Bug report

Gordano GMS

POP3/IMAP

Unfixed

CVE-2021-37844

recvmail

SMTP

Fixed in 3.1.2 (reported privately)

\-

SmarterMail

POP3

Fixed in Build 7537

CVE-2020-29548

Burp Collaborator

SMTP

Fixed in 2020.9.2

Bug report, Vendor release notes

Dovecot

SMTP

Fixed in 2.3.14.1 and 2.3.15

CVE-2021-33515

Mercury/32

SMTP/POP3/IMAP

Fixed in 4.90

CVE-2021-33487

QMail Toaster (1.4.1)

SMTP

Project discontinued

\-

Courier

POP3

Fixed in 1.1.5 (reported privately), known since 2013

Discussion from 2013, CVE-2021-38084, Fix

PHP (stream\_socket\_enable\_crypto)

SMTP/POP3/IMAP

Unfixed

Bug report (private)

**Session Fixation**

Product

Protocol

Status

Links

Citadel

POP3/IMAP

Reported via forum, unfixed

Forum with report, CVE-2021-37845

IPswitch iMail

POP3/IMAP

Fixed in iMail 12.5.8

CVE-2021-37846, Changelog

**Miscellaneous Issues**

Product

Protocol

Description

Status

Links

Nemesis (used by GMX / Web.de, provider)

SMTP

Advertises authentication before STARTTLS even though it is disabled

Fixed (reported via Bugbounty)

\-

**Media reports**

Golem.de: Sicherheitsrisiko STARTTLS  
The Hacker News: Dozens of STARTTLS Related Flaws Found Affecting Popular Email Clients  
The Record: STARTTLS implementations in email clients & servers plagued by 40+ vulnerabilities  
SecurityLab.ru: Десятки уязвимостей в протоколе STARTTLS затрагивают популярные почтовые клиенты  
LWN: STARTTLS considered harmful  
Bulletproof TLS Newsletter: Vulnerabilities show fragility of STARTTLS  
APNIC blog: Vulnerabilities show why STARTTLS should be avoided if possible  

**Presentations**

USENIX Security '21 - Why TLS is better without STARTTLS  
Driving IT Conference 2021: STARTTLS endangers your E-Mail passwords  

**Followup research**

After we published our research some people found similar bugs in other protocols using STARTTLS.

StartTLS in LDAP  
nbdkit: Reset structured replies on STARTTLS (CVE-2021-3716)  
fetchmail: STARTTLS session encryption bypassing (CVE-2021-39272)  
curl 7.79.0 fixes two STARTTLS vulnerabilities  
CVE-2021-38542: Apache James vulnerable to STARTTLS command injection (IMAP and POP3)

Tag

#samsung