Cisco Systems has disclosed a denial-of-service vulnerability in its Cisco Secure Firewall ASA and Cisco Secure Firewall FTD products. The flaw, identified as CVE-2026-76418, affects the SSL VPN remote access functionality and has already been observed in active exploitation.
The vulnerability impacts configurations where secondary authentication is enabled on tunnel groups within the SSL VPN login service. An unauthenticated attacker can send a specially crafted request during the VPN connection process, triggering an immediate device reboot and resulting in a service denial condition.
According to the Common Vulnerability Scoring System, the issue received a base score of 8.6 under CVSS v3.1, placing it in the High severity category. Cisco published the security advisory on October 28, 2026, and confirmed that exploitation attempts were detected during the same month.
Patches that resolve the vulnerability are now available for both Cisco Secure Firewall ASA and Cisco Secure Firewall FTD. The vendor strongly urges administrators to apply the updates without delay to restore protection against remote denial-of-service attacks.
