CVE-2026-20154 Denial of service in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
Remote attackers can cause denial of service on Cisco ASA and FTD devices by flooding SYN packets, leading to high CPU utilization.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20154?
CVE-2026-20154 is a high-severity denial of service vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-835
Which versions are affected by CVE-2026-20154?
How do I fix CVE-2026-20154?
No fix has been published for CVE-2026-20154 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-20154 being exploited?
There is no known exploitation of CVE-2026-20154 in the wild and no public exploit code.
Sources
Also known as GHSA-fcpc-64j2-96jc.