CVE-2026-20295 Denial of service in Cisco Secure Firewall Management Center (FMC)
Unauthenticated remote attackers can cause denial of service by exhausting memory via crafted sftunnel TLS frames in Cisco Secure Firewall Management Center and Threat Defense.
- 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-2026-20295?
CVE-2026-20295 is a high-severity denial of service vulnerability in Cisco Secure Firewall Management Center (FMC), 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 sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, remote attacker to exhaust the available memory of an affected device. This vulnerability is due to improper management of memory resources during sftunnel TLS connection setup. An attacker could exploit this vulnerability by sending crafted sftunnel TLS frames to an affected device during the connection setup. A successful exploit could allow the attacker to exhaust the available memory on the affected device, which could result in a DoS condition.
Weakness: CWE-789
Which versions are affected by CVE-2026-20295?
How do I fix CVE-2026-20295?
No fix has been published for CVE-2026-20295 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-2026-20295 being exploited?
There is no known exploitation of CVE-2026-20295 in the wild and no public exploit code.
Sources
Also known as GHSA-2x4m-98h8-xp8g.