Cisco Firewall Zero-Day Exploited for DoS Attacks

EXECUTIVE SUMMARY:

A critical vulnerability, tracked as CVE-2026-20349 with a CVSS score of 9.8, affects Secure Firewall ASA and FTD devices, allowing remote attackers to cause an appliance to reload and enter a denial-of-service (DoS) condition by sending a specially crafted HTTP request to the Remote Access SSL VPN service without authentication. This flaw type is related to the processing of HTTP requests and could enable threat actors to disrupt security appliances, potentially preventing them from detecting and blocking further malicious activity. The business impact of this vulnerability includes disruption of security services, allowing potential malicious activity to go undetected. Cisco has released patches for this zero-day vulnerability and customers have been urged to apply available hotfixes as soon as possible.

RECOMMENDATION:

We recommend you refer below mention link to apply patches: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-dzv4mQFF[emaillocker id="1283"]

REFERENCES:

The following reports contain further technical details:

• https://www.securityweek.com/cisco-patches-firewall-zero-day-exploited-for-dos-attacks/