Cisco Secure Firewall Vulnerability Exposes Systems to Remote Code Execution by Attackers

Cisco has released emergency updates for CVE-2026-20131, a critical (CVSS 10.0) insecure Java deserialization vulnerability in Secure Firewall Management Center and SCC Firewall Management that permits unauthenticated remote arbitrary code execution as root; attackers are observed exploiting it in the wild (March 2026), there are no practical workarounds for on-prem FMC deployments, Cisco has deployed hotfixes for its SaaS SCC service, and administrators are urged to apply the fixed releases immediately.