CVE-2026-20290 Cisco Secure Firewall Threat Defense Software Snort 2 SSL/TLS Denial of Service Vulnerability
An unauthenticated remote attacker can cause a denial of service by sending a crafted SSL connection request to the Snort 2 Detection Engine.
- 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-2026-20290?
CVE-2026-20290 is a medium-severity denial of service vulnerability in Cisco Secure Firewall Threat Defense (FTD) 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 SSL/TLS certificate parsing in the Snort 2 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 2 Detection Engine to restart. This vulnerability is due to incomplete validation of the SSL certificate. An attacker could exploit this vulnerability by sending a crafted SSL connection setup request to be parsed by Snort 2. A successful exploit could allow the attacker to cause the Snort 2 Detection Engine to restart unexpectedly, resulting in a denial of service (DoS) condition.
Weakness: CWE-805
Which versions are affected by CVE-2026-20290?
How do I fix CVE-2026-20290?
No fix has been published for CVE-2026-20290 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-2026-20290 being exploited?
There is no known exploitation of CVE-2026-20290 in the wild and no public exploit code.
Sources
Also known as GHSA-xxfc-5fpg-3fhq.