Cisco Secure Firewall Adaptive Security Appliance Software Remote Access SSL VPN memory leak

Summaryinfo

A vulnerability described as problematic has been identified in Cisco Secure Firewall Adaptive Security Appliance Software and Secure Firewall Threat Defense Software. This vulnerability affects unknown code of the component Remote Access SSL VPN. The manipulation results in memory leak. This vulnerability is known as CVE-2026-20105. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, was found in Cisco Secure Firewall Adaptive Security Appliance Software and Secure Firewall Threat Defense Software (unknown version). Affected is an unknown code block of the component Remote Access SSL VPN. The manipulation with an unknown input leads to a memory leak vulnerability. CWE is classifying the issue as CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. This is going to have an impact on availability. CVE summarizes:

A vulnerability in the Remote Access SSL VPN functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker with a valid VPN connection to exhaust device memory resulting in a denial of service (DoS) condition.This does not affect the management or MUS interfaces. 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 reload, resulting in a DoS condition.

The advisory is shared for download at sec.cloudapps.cisco.com. This vulnerability is traded as CVE-2026-20105 since 10/08/2025. The exploitability is told to be easy. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 03/04/2026). The MITRE ATT&CK project declares the attack technique as T1499.

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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