Cisco ASA/FTD flaw lets attackers crash firewalls, CVE-2026-20349

A critical vulnerability in Cisco's Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) has been identified, tracked as CVE-2026-20349. This flaw allows unauthenticated attackers to remotely crash the firewall, designated with a CVSS score of 8.6 (High). The vulnerability affects multiple versions of the ASA and FTD software and is already being actively exploited. Cisco recommends urgent upgrading to fixed releases, as no workarounds are available. The flaw arises from weak input validation in the Remote Access SSL VPN service, enabling denial of service conditions.