Warning: Actively Exploited DoS vulnerability in Cisco Secure Firewall, Patch Immediately!

This advisory describes CVE-2026-20349, a heap-inspection/clearing vulnerability in Cisco Secure Firewall ASA and FTD software that can be exploited by an unauthenticated remote attacker via crafted HTTP requests to force device reloads (DoS). The vulnerability has a CVSS 3.1 score of 8.6, is actively exploited, affects multiple ASA/FTD versions and specific VPN/zero-trust configurations, and the report urges immediate patching and increased detection/monitoring.