A Vulnerability in Cisco Secure Firewall ASA and FTD Could Allow for Denial of Service

A vulnerability has been discovered in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software that could allow for denial of service (DoS). Cisco Secure Firewall ASA and FTD provide firewall, VPN, and threat defense capabilities for enterprise environments. An attacker could exploit this vulnerability by sending a specially crafted request when connecting to a vulnerable SSL remote access VPN service that has secondary authentication configured on a tunnel group.

Successful exploitation could cause the affected device to reload unexpectedly, resulting in a DoS condition and interruption of remote access services. Cisco has released software updates to address this vulnerability, and Cisco states that no workarounds address this vulnerability, though a temporary mitigation is available.

CVE-2026-76418 has been publicly disclosed and is being actively exploited in the wild.

A vulnerability has been discovered in Cisco Secure Firewall ASA Software and Cisco Secure Firewall Threat Defense Software that could allow for denial of service. The vulnerability exists in the Remote Access SSL VPN service and is caused by logic errors when secondary authentication is configured on a tunnel group. Details of the vulnerability are as follows:

Tactic:Initial Access(TA0001):

Technique:Exploit Public-Facing Application(T1190):

Tactic: Impact (TA0040):

Technique:Endpoint Denial of Service(T1499):

Sub-technique: Application or System Exploitation(T1499.004):

Successfulexploitation of this vulnerability could result in a DoS condition, disrupting remote access VPN connectivity and availability. Cisco states that no workarounds address this vulnerability, though a temporary mitigation is available. Cisco strongly recommends upgrading to a fixed release. Organizations should review the Cisco advisory listed in the References section for mitigation details and evaluate them before deployment.

We recommend the following actions be taken:

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