Cisco FMC CVE-2026-20079 Actively Exploited

CVE-2026-20079 is an authentication bypass (CWE-288) in the web interface of Cisco Secure Firewall Management Center (FMC) Software, caused by an improper system process created at boot time. An unauthenticated, remote attacker can exploit it by sending crafted HTTP requests to the FMC web interface, which allows the execution of script files and commands on the device. A successful exploit grants the attacker root access to the underlying operating system, giving full control of the management platform (CVSS 3.1: 10.0, network-exploitable, no privileges or user interaction required, scope changed). The flaw affects Cisco Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management deployments. Cisco has confirmed the vulnerability is being exploited in active attacks, it carries a 35.9% EPSS score (98th percentile), and CISA added it to the Known Exploited Vulnerabilities catalog on 2026-09-09.

Do: Upgrade FMC (and SCC Firewall Management tenants) to the fixed release specified in Cisco's advisory, prioritizing internet-exposed or externally reachable management interfaces; CISA KEV action applies to federal agencies under BOD 26-04. Until patching, restrict FMC web interface access to trusted management networks and VPNs and check devices for signs of exploitation such as unexpected script execution, unfamiliar processes, or root-level changes. Triage per CISA's Forensics Triage Requirements if compromise is suspected.