Cisco Secure Firewall Adaptive Security Appliance Remote Access SSL VPN service denial of service

Summaryinfo

A vulnerability classified as critical has been found in Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense. The affected element is an unknown function of the component Remote Access SSL VPN service. This manipulation causes denial of service. This vulnerability appears as CVE-2026-76418. The attack may be initiated remotely. In addition, an exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense (version now known). Affected by this vulnerability is some unknown processing of the component Remote Access SSL VPN service. The manipulation with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. The summary by CVE is:

A vulnerability in the Remote Access SSL VPN service of 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 logic errors when secondary authentication is configured on a tunnel group. An attacker could exploit this vulnerability by sending a crafted request when connecting to the SSL remote access VPN. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

It is possible to read the advisory at sec.cloudapps.cisco.com. This vulnerability is known as CVE-2026-76418 since 08/19/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are unknown but an exploit is available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/29/2026). The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

It is declared as attacked. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 10/29/2026 with a due date of 11/01/2026:

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BO

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Firewall Software

Vendor

• Cisco

Name

• Secure Firewall Adaptive Security Appliance
• Secure Firewall Threat Defense

License

• commercial

Website

• Vendor: https://www.cisco.com/

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