Cisco Security Advisory
Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Remote Access SSL VPN Multiple Certificate Authentication Bypass Vulnerability
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CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X
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A vulnerability in the remote access SSL VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, remote attacker to bypass a configured multiple certificate authentication policy and connect using only a valid username and password.
This vulnerability is due to improper error handling during remote access VPN authentication. An attacker could exploit this vulnerability by sending crafted requests during remote access VPN session establishment. A successful exploit could allow the attacker to bypass the configured multiple certificate authentication policy while retaining the privileges and permissions associated with the original connection profile.
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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-multi-cert-dzA3h5PTThis 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.
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Vulnerable Products
At the time of publication, this vulnerability affected Cisco devices if they were running a vulnerable release of Cisco ASA Software or FTD Software and had the remote access SSL VPN feature enabled with at least one configuration profile requiring multiple certificate authentication.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine the Remote Access SSL VPN Configuration
To determine the remote access VPN configuration, use the show running-config webvpn | include ^ enable CLI command. If the command returns output, the remote access SSL VPN feature is enabled on the listed interface(s). Empty output indicates that the remote access SSL VPN feature is not enabled. The following example shows the output of the show running-config webvpn | include ^ enable command on a device that has the remote access SSL VPN feature enabled on the outside interface:
asa# show running-config webvpn | include ^ enable
enable outsideIf the remote access SSL VPN feature is enabled on at least one interface, use the show running-config tunnel-group | include multiple-certificate CLI command to assess whether a connection profile requiring multiple certificate authentication is configured. If the command returns output, at least one configuration profile requiring multiple certificate authentication is configured. Empty output indicates that multiple certificate authentication is not used on the device. The following example shows the output of the show running-config tunnel-group | include multiple-certificate command on a device that has one configuration profile requiring multiple certificate authentication configured:
asa# show running-config tunnel-group | include multiple-certificate
authentication multiple-certificateIf one or both of the above commands return empty output, the device is not affected by this vulnerability.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following Cisco products:
- Firepower Management Center (FMC) Software
- IOS Software
- IOS XE Software
- IOS XR Software
- Next-Generation Intrusion Prevention System (NGIPS) Software
- NX-OS Software
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There are no workarounds that address this vulnerability.
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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:
- Choose which advisories the tool will search-all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.
- Choose the appropriate software.
- Choose the appropriate platform.
- Enter a release number-for example, 9.16.2.11 for Cisco ASA Software or 6.6.7 for Cisco FTD Software.
- 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
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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.
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Cisco would like to thank Tobias Moritz of Deutsche Telekom MMS GmbH for reporting this vulnerability.
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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.
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Show LessVersion Description Section Status Date 1.0 Initial public release. - Final 2023-NOV-01
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