CVE-2026-20349 is a high-severity vulnerability (CVSS 8.6), listed in the CISA Known Exploited Vulnerabilities (KEV) catalog as actively exploited.
Summary
A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.
This vulnerability is due to insufficient error checking when processing HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the Remote Access SSL VPN service on an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
Remediation
It is actively exploited — apply the vendor’s patch immediately and prioritize internet-facing systems. Patch-management tools that can deploy and verify the fix include Action1, Automox, ManageEngine Patch Manager Plus, ManageEngine Endpoint Central. See our best patch management ranking.