Cisco Secure Firewall Adaptive Security Appliance Software Access SSL VPN/HTTP Management/MUS memory leak

Summaryinfo

A vulnerability classified as problematic has been found in Cisco Secure Firewall Adaptive Security Appliance Software and Secure Firewall Threat Defense Software. This issue affects some unknown processing of the component Access SSL VPN/HTTP Management/MUS. This manipulation causes memory leak. This vulnerability is handled as CVE-2026-20106. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Cisco Secure Firewall Adaptive Security Appliance Software and Secure Firewall Threat Defense Software (version now known) and classified as problematic. Affected by this vulnerability is some unknown processing of the component Access SSL VPN/HTTP Management/MUS. The manipulation with an unknown input leads to a memory leak vulnerability. The CWE definition for the vulnerability is CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. As an impact it is known to affect availability. The summary by CVE is:

A vulnerability in the Remote Access SSL VPN, HTTP management and MUS functionality, of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to exhaust device memory resulting in a denial of service (DoS) condition requiring a manual reboot. This vulnerability is due to trusting user input without validation. An attacker could exploit this vulnerability by sending crafted packets to the Remote Access SSL VPN server. A successful exploit could allow the attacker to cause the device to stop responding, resulting in a DoS condition.

The advisory is shared at sec.cloudapps.cisco.com. This vulnerability is known as CVE-2026-20106 since 10/08/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 03/04/2026). MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Firewall Software

Vendor

• Cisco

Name

• Secure Firewall Adaptive Security Appliance Software
• Secure Firewall Threat Defense Software

License

• commercial

Website

• Vendor: https://www.cisco.com/

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