Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software SSL VPN Denial of Service Vulnerability

Description

Update for September 16, 2026: The original 1.0 version of this advisory was specific to the Cisco Adaptive Security Virtual Appliance (ASAv) and Cisco Secure Firewall Threat Defense Virtual (FTDv) models. However, it was later found that this vulnerability affects all Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software platforms. A vulnerability in the VPN and management web servers of the Cisco Secure Firewall ASA Software and Cisco Secure FTD Software platforms could allow an unauthenticated, remote attacker to cause an affected device to run out of system memory or buffer blocks, which in turn could cause SSL VPN connection processing to slow down and eventually cease altogether. This vulnerability is due to a lack of proper memory management for new incoming SSL/TLS connections. An attacker could exploit this vulnerability by sending a large number of new incoming SSL/TLS connections to the targeted device. A successful exploit could allow the attacker to deplete system memory or buffers, resulting in a denial of service (DoS) condition. The memory or buffers could be reclaimed slowly if the attack traffic is stopped, but a manual reload may be required to restore operations quickly. 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-asaftdvirtual-dos-MuenGnYR This advisory is part of the October 2024 release of the Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: October 2024 Semiannual Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication . Security Impact Rating: High CVE: CVE-2024-20260

What to do

Install the fixed versions listed in the official advisory. If you cannot update right away, apply the workarounds or mitigations it describes and limit access to the affected service.

Details

Vendor

Cisco

Product

Cisco ASA / FTD

CVE

CVE-2024-20260

Affected versions

Cisco Secure Firewall Adaptive Security Appliance (ASA) Soft 9.16: 37 versions, from 9.16.1 to 9.16.4.92
Cisco Secure Firewall Adaptive Security Appliance (ASA) Soft 9.18: 28 versions, from 9.18.1 to 9.18.4.68
Cisco Secure Firewall Adaptive Security Appliance (ASA) Soft 9.19: 13 versions, from 9.19.1 to 9.19.1.42
Cisco Secure Firewall Adaptive Security Appliance (ASA) Soft 9.20: 19 versions, from 9.20.1 to 9.20.4.19
Cisco Secure Firewall Adaptive Security Appliance (ASA) Soft 9.23: 6 versions, from 9.23.1 to 9.23.1.22
Cisco Secure Firewall Adaptive Security Appliance (ASA) Soft 9.22: 10 versions, from 9.22.1.1 to 9.22.2.20
Cisco Secure Firewall Threat Defense (FTD) Software 7.0: 17 versions, from 7.0.0 to 7.0.9
Cisco Secure Firewall Threat Defense (FTD) Software 7.2: 17 versions, from 7.2.0 to 7.2.10.2
Cisco Secure Firewall Threat Defense (FTD) Software 7.3: 4 versions, from 7.3.0 to 7.3.1.2
Cisco Secure Firewall Threat Defense (FTD) Software 7.4: 9 versions, from 7.4.0 to 7.4.3
Cisco Secure Firewall Threat Defense (FTD) Software 7.6: 5 versions, from 7.6.0 to 7.6.4
Cisco Secure Firewall Threat Defense (FTD) Software 7.7: 4 versions, from 7.7.0 to 7.7.11 (from the advisory and NVD; check the exact builds in the official advisory)

CVSS score

8.6

Actively exploited

Not known at this time

Source

Cisco PSIRT – original advisory

Published

September 23, 2026

The description and the recommended action are quoted from the public advisory (the action is our generic advice); severity, exploitation status and affected versions are compiled automatically from public sources and may contain errors. The vendor's original advisory prevails: check it before taking action. This information is provided without warranty and does not replace a professional assessment.