A vulnerability in the remote access SSL VPN features of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper validation of errors that are logged as a result of client connections that are made using remote access VPN. An attacker could exploit this vulnerability by sending crafted requests to an affected system. A successful exploit could allow the attacker to cause the affected device to restart, resulting in a DoS condition. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link:https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-dos-tL4uA4AA This advisory is part of the April 2022 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: April 2022 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.
A vulnerability in the remote access SSL VPN features of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to improper validation of errors that are logged as a result of client connections that are made using remote access VPN. An attacker could exploit this vulnerability by sending crafted requests to an affected system. A successful exploit could allow the attacker to cause the affected device to restart, resulting in a DoS condition.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-dos-tL4uA4AA
This advisory is part of the April 2022 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: April 2022 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.
This vulnerability affects Cisco products if they are running a vulnerable release of Cisco ASA Software or FTD Software and have a vulnerable AnyConnect or WebVPN configuration.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
To determine whether the software on a device has a vulnerable feature configured, use the show-running-config CLI command. In the following table, the left column lists the Cisco ASA Software features that are vulnerable. The right column shows the output of the show running-config CLI command on a device that has the feature enabled. If a device is running a vulnerable release and has one of these features configured, it is affected by this vulnerability.
| Cisco ASA Software Feature | Vulnerable Configuration |
|---|---|
| AnyConnect SSL VPN |
webvpn |
| Clientless SSL VPN |
webvpn |
To determine whether the software on a device has a vulnerable feature configured, use the show-running-config CLI command. In the following table, the left column lists the Cisco FTD Software features that are vulnerable. The right column shows the output of the show running-config CLI command on a device that has the feature enabled. If a device is running a vulnerable release and has one of these features configured, it is affected by this vulnerability.
| Cisco FTD Software Feature | Vulnerable Configuration |
|---|---|
| AnyConnect SSL VPN1,2 |
webvpn |
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
There are no workarounds that address this vulnerability.
Cisco has released free software updates that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.
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.
The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.
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.
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.
In the following table(s), the left column lists Cisco software releases. 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 any of the Critical or High SIR vulnerabilities described in this bundle and which release includes fixes for those vulnerabilities.
ASA Software
| Cisco ASA Software Release | First Fixed Release for This Vulnerability | First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories |
|---|---|---|
| 9.15 and earlier1 | Not vulnerable. | 9.15.1.21 |
| 9.16 | 9.16.2.11 | 9.16.2.14 |
| 9.17 | 9.17.1 | 9.17.1.7 |
FTD Software
| Cisco FTD Software Release | First Fixed Release for This Vulnerability | First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories |
|---|---|---|
| 6.2.2 and earlier1 | Not vulnerable. | Migrate to a fixed release. |
| 6.2.3 | Not vulnerable. | Migrate to a fixed release. |
| 6.3.01 | Migrate to a fixed release. | Migrate to a fixed release. |
| 6.4.0 | 6.4.0.13 | 6.4.0.15 (May 2022) |
| 6.5.01 | Migrate to a fixed release. | Migrate to a fixed release. |
| 6.6.0 | 6.6.5.2 | 6.6.5.2 |
| 6.7.0 | Cisco_FTD_Hotfix_AA-6.7.0.4-2.sh.REL.tar Cisco_FTD_SSP_FP1K_Hotfix_AA-6.7.0.4-2.sh.REL.tar Cisco_FTD_SSP_FP2K_Hotfix_AA-6.7.0.4-2.sh.REL.tar Cisco_FTD_SSP_Hotfix_AA-6.7.0.4-2.sh.REL.tar |
Migrate to a fixed release. |
| 7.0.0 | 7.0.2 (May 2022) | 7.0.2 (May 2022) |
| 7.1.0 | 7.1.0.1 | 7.1.0.1 |
For instructions on upgrading your FTD device, see Cisco Firepower Management Center Upgrade Guide.
The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
This vulnerability was found during the resolution of a Cisco TAC support case.
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.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2022-APR-27 |
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