Cisco Security Advisory
Cisco Adaptive Security Appliance and Firepower Threat Defense Software VPN Web Client Services Client-Side Request Smuggling Vulnerability
A vulnerability in the VPN web client services component of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct browser-based attacks against users of an affected device.
This vulnerability is due to improper validation of input that is passed to the VPN web client services component before being returned to the browser that is in use. An attacker could exploit this vulnerability by persuading a user to visit a website that is designed to pass malicious requests to a device that is running Cisco ASA Software or Cisco FTD Software and has web services endpoints supporting VPN features enabled. A successful exploit could allow the attacker to reflect malicious input from the affected device to the browser that is in use and conduct browser-based attacks, including cross-site scripting attacks. The attacker could not directly impact the affected device.
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:
At the time of publication, this vulnerability affected Cisco products if they were running a vulnerable release of the following Cisco software:
- ASA Software with Cisco AnyConnect VPN or Clientless SSL VPN enabled
- FTD Software with Cisco AnyConnect VPN enabled
See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.
Determine the ASA Software Configuration
To determine whether the software has a vulnerable feature enabled, 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 indicates the basic configuration for each feature from the show running-config CLI command. If a device is running a vulnerable release and has one of these features enabled, it is vulnerable.
Cisco ASA Feature Vulnerable Configuration AnyConnect Internet Key Exchange Version 2 Remote Access (with client services)
crypto ikev2 enable client-services port
AnyConnect SSL VPN
Clientless SSL VPN
Determine the FTD Software Configuration
To determine whether the software has a vulnerable feature enabled, 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 indicates the basic configuration for each feature from the show running-config CLI command. If a device is running a vulnerable release and has one of these features enabled, it is vulnerable.
Cisco FTD Feature Vulnerable Configuration AnyConnect Internet Key Exchange Version 2 Remote Access (with client services)1,2
crypto ikev2 enable client-services port
AnyConnect SSL VPN1,2
enable1. Remote Access VPN features were introduced in Cisco FTD Software Release 184.108.40.206. Remote Access VPN features are enabled by using Devices > VPN > Remote Access in Cisco Firepower Management Center (FMC) or by using Device > Remote Access VPN in Cisco Firepower Device Manager (FDM).
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 devices with remote access VPN services that are configured to accept only AnyConnect Internet Key Exchange Version 2 Remote Access VPN with client services disabled are not affected by this vulnerability.
There are no workarounds that address this vulnerability.
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, 220.127.116.11 for Cisco ASA Software or 6.6.7 for Cisco FTD Software.
- Click Check.
The Cisco Product Security Incident Response Team (PSIRT) is aware that proof-of-concept exploit code is available for the vulnerability described in this advisory.
The Cisco PSIRT is not aware of any malicious use of the vulnerability that is described in this advisory.
Cisco would like to thank James Kettle of Portswigger.net for reporting this vulnerability.
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 2.1 Updated information about fixed software availability. Summary, Fixed Software Final 2022-DEC-16 2.0 Added FTD Software as an affected product. Updated the affected VPN component. Clarified affected software configurations. Removed the mitigation because it no longer applies. Title, Summary, Vulnerable Products, Products Confirmed Not Vulnerable, and Workarounds Final 2022-NOV-09 1.0 Initial public release. - Final 2022-AUG-10
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