CVE-2026-20249 Denial of service in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
Remote attackers can crash the IKEv2 process on Cisco ASA and FTD devices by sending crafted certificates, causing a denial of service.
- 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-2026-20249?
CVE-2026-20249 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 certification authentication feature of Internet Key Exchange version 2 (IKEv2) for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly. This vulnerability is due to a logic error during the certificate authentication phase of the IKEv2 connection setup. An attacker could exploit this vulnerability by attempting to establish an IKEv2 VPN connection with a crafted certificate. A successful exploit could allow the attacker to cause the IKEv2 process to crash, causing a denial of service (DoS) condition.
Weakness: CWE-704
Which versions are affected by CVE-2026-20249?
How do I fix CVE-2026-20249?
No fix has been published for CVE-2026-20249 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-2026-20249 being exploited?
There is no known exploitation of CVE-2026-20249 in the wild and no public exploit code.
Sources
Also known as GHSA-q3fg-q5c4-7677.