CVE-2026-20336

CVE-2026-20336 is an improper control of a resource through its lifetime (CWE-664) in Cisco Secure Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, and Cisco Secure Firewall Management Center (FMC) Software, discovered internally during a comprehensive Cisco security review and addressed in a software hardening release. The flaw is exploitable from an adjacent network (CVSS AV:A) without privileges or user interaction, and successful exploitation could yield high-impact confidentiality, integrity, and availability compromise on the affected appliance or management platform. Cisco ASA and FTD are among the most widely deployed enterprise firewall platforms, and FMC is the central manager for FTD fleets, so most organizations running these products are in scope. There is currently no public proof-of-concept, no known in-the-wild exploitation, and the issue is not on CISA's Known Exploited Vulnerabilities catalog.

What to do: Check Cisco's PSIRT advisory for CVE-2026-20336 to identify the hardening release covering your ASA, FTD, and FMC version trains, and upgrade accordingly. Because the attack vector is adjacent (AV:A), restrict management and VPN-facing interfaces to trusted network segments and limit L2/L3 adjacency to untrusted devices in the meantime. ASA/FTD/FMC bundles frequently ship related fixes, so apply the full hardening release rather than cherry-picking individual CVEs.