CVE-2026-20154: Cisco Secure Firewall Adaptive Security Appliance ASA Software

High severity, CVSS 8.6. EPSS: 0.4% chance of exploitation in the next 30 days.

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. 

Affected products

• Cisco Cisco Secure Firewall Adaptive Security Appliance ASA Software: version 9.16.1 only; version 9.16.1.28 only; version 9.16.2 only; version 9.16.2.3 only; version 9.16.2.7 only; version 9.16.2.11 only; …
• Cisco Cisco Secure Firewall Threat Defense FTD Software: version 7.0.0 only; version 7.0.0.1 only; version 7.0.1 only; version 7.0.1.1 only; version 7.0.2 only; version 7.2.0 only; …

Published 2026-09-16. Last modified 2026-09-18.