A high-severity flaw in the Remote Access SSL VPN service of Cisco Secure Firewall Adaptive Security Appliance (ASA) and Cisco Secure Firewall Threat Defense (FTD) is under active exploitation to crash vulnerable devices.
The vulnerability, tracked as CVE-2026-76418 and rated 8.6 in severity, is due to logic errors when secondary authentication is configured on a tunnel group, Cisco said in its advisory. It could allow a remote, unauthenticated attacker to send a crafted request when connecting to the SSL remote access VPN that results in a device reload and thus denial of service.
Vulnerable products
“If the running configuration contains the webvpn keyword and SSL VPN is enabled on at least one interface, the configuration is vulnerable,” the advisory said. “If tunnel-group-list enable is configured, check all tunnel groups, including the default tunnel group, DefaultWEBVPNGroup, for secondary-authentication-server-group. If tunnel-group-list enable is absent or has been removed using the no tunnel-group-list enable command, check the default tunnel group, DefaultWEBVPNGroup, for secondary-authentication-server-group because disabling the group list does not remove exposure when that default group uses secondary authentication.”
