CVE-2026-20323 Auth bypass in Cisco Secure Firewall Management Center (FMC)
An adjacent attacker can bypass authentication in Cisco FMC/FTD sftunnel using a crafted TLS certificate to gain root access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20323?
CVE-2026-20323 is a high-severity authentication bypass vulnerability in Cisco Secure Firewall Management Center (FMC), published on 16 Sep 2026. It can only be exploited from the same machine or local network, 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, adjacent attacker to impersonate the peer device and obtain access at the level of the manager role, which is equivalent to root. This vulnerability is due to improper management of the TLS certificate for the sftunnel management connection. An attacker could exploit this vulnerability by connecting to the sftunnel port using a crafted TLS certificate. A successful exploit could allow the attacker to become a registered sftunnel peer with root access. Note: The attack is successful only if the sftunnel connection is down or the attack can disrupt the sftunnel connection long enough to execute the attack.
Weakness: CWE-295
Which versions are affected by CVE-2026-20323?
How do I fix CVE-2026-20323?
No fix has been published for CVE-2026-20323 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-20323 being exploited?
There is no known exploitation of CVE-2026-20323 in the wild and no public exploit code.
Sources
Also known as GHSA-f2cp-mvp8-7wp4.