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

Description

A vulnerability in the system rate-limiting process for syslog message 419002 of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause high CPU utilization on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improper rate limiting for syslog message 419002. An attacker could exploit this vulnerability by sending a flood of TCP synchronization (SYN) packets to an affected device. A successful exploit could allow the attacker to cause high CPU utilization, resulting in performance degradation. Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability. This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-logging-dos-ZXXNesfN This advisory is part of a group of advisories. For a complete list of the advisories and links to them, see Cisco Advance Notification for Publication of September 16, 2026, Security Advisories . In addition, for further documentation of improvements and fixes in Cisco Secure Firewall products, see Cisco Secure Firewall Adaptive Security Appliance Software, Secure Firewall Threat Defense Software, and Secure Firewall Management Center Software Hardening Release: September 2026 . Security Impact Rating: High CVE: CVE-2026-20154

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-2026-20154

Affected versions

Cisco Secure Firewall Adaptive Security Appliance (ASA) Soft 9.16: 35 versions, from 9.16.1 to 9.16.4.85
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: 18 versions, from 9.20.1 to 9.20.4.14
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: 16 versions, from 7.0.0 to 7.0.8.1
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: 10 versions, from 7.4.0 to 7.4.4
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 18, 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.