Summary

• A vulnerability in the VPN web services component of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall 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 HTTP requests. An attacker could exploit this vulnerability by persuading a user to visit a website that is designed to pass malicious HTTP requests to a device that is running Cisco Secure Firewall ASA Software or Cisco Secure 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 (XSS) attacks. The attacker is not able to 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:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-desync-n5AVzEQw

  This advisory is part of the March 2026 release of the Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: March 2026 Semiannual Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco products if they were running a vulnerable release of Cisco Secure Firewall ASA Software or Secure FTD Software with one or both of the following features configured:

  • Internet Key Exchange version 2 (IKEv2) Remote Access VPN with client services
  • SSL VPN

  Note: Devices with remote access VPN services that are configured to accept only IKEv2 Remote Access VPN and have IKEv2 client services disabled are not affected by this vulnerability.

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

  Determine the Device 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 Secure Firewall ASA Software or Secure 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 considered vulnerable.

  Cisco Secure Firewall ASA Software or Secure FTD Software Feature	Vulnerable Configuration
  IKEv2 Remote Access VPN (with client services)1	crypto ikev2 enable client-services port
  SSL VPN1	webvpn enable

  1. For Cisco Secure FTD Software, remote access VPN features are enabled from Devices > VPN > Remote Access in Cisco Secure Firewall Management Center (FMC) Software or from Remote Access VPN in Cisco Secure Firewall 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 this vulnerability does not affect Cisco Secure FMC Software.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• Cisco considers any workarounds and mitigations (if applicable) to be temporary solutions until an upgrade to a fixed software release is available. To fully remediate this vulnerability and avoid future exposure as described in this advisory, Cisco strongly recommends that customers upgrade to the fixed software indicated in this advisory.

  Cisco Secure Firewall ASA, Secure FMC, and Secure FTD Software

  To help customers determine their exposure to vulnerabilities in Cisco Secure Firewall ASA, Secure FMC, and Secure 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:

  1. Choose which advisories the tool will search—all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.
  2. Choose the appropriate software.
  3. Choose the appropriate platform.
  4. Enter a release number—for example, 9.20.3.4 for Cisco Secure Firewall ASA Software or 7.4.2 for Cisco Secure FTD Software.
  5. Click Check.

  Only this advisoryAll Critical and High advisoriesAll advisoriesCisco ASA SoftwareCisco FMC SoftwareCisco FTD SoftwareAny Platform3000 Series Industrial Security Appliances (ISA)ASA 5500-X Series FirewallsASA Service ModuleAdaptive Security Virtual Appliance (ASAv)Firepower 1000 SeriesFirepower 2100 SeriesFirepower 4100 SeriesFirepower 9000 SeriesSecure Firewall 1200 SeriesSecure Firewall 3100 SeriesSecure Firewall 4200 Series

   

  For instructions on upgrading a Cisco Secure FTD device, see the appropriate Cisco Secure FMC upgrade guide.

  Additional Resources

  For help determining the best Cisco Secure Firewall ASA, Secure FMC, or Secure FTD Software release, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

  Cisco Secure Firewall ASA Compatibility
  Cisco Secure Firewall ASA Upgrade Guide
  Cisco Secure Firewall Threat Defense Compatibility Guide

Exploitation and Public Announcements

• 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.

Source

• Cisco would like to thank Josh Weber of NetSPI for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-desync-n5AVzEQw

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2026-MAR-04

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