CVE-2025-20133

A vulnerability in the management and VPN web servers of the Remote Access SSL VPN feature of Cisco Secure Firewall ASA Software and Secure FTD Software could allow an unauthenticated, remote attacker to cause the device to unexpectedly stop responding, resulting in a DoS condition. This vulnerability is due to ineffective validation of user-supplied input during the Remote Access SSL VPN authentication process. An attacker could exploit this vulnerability by sending a crafted request to the VPN service on an affected device. A successful exploit could allow the attacker to cause a DoS condition where the device stops responding to Remote Access SSL VPN authentication requests.

Scoring

Severity

HIGH

CVSS base score

8.6

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS probability

0.74%

CWE

CWE-401

Published

2025-08-14

Last modified

2026-03-12

Affected products

• Cisco Cisco Adaptive Security Appliance (ASA) Software
• Cisco Cisco Adaptive Security Appliance (ASA) Software
• Cisco Cisco Adaptive Security Appliance (ASA) Software
• Cisco Cisco Adaptive Security Appliance (ASA) Software
• Cisco Cisco Adaptive Security Appliance (ASA) Software
• Cisco Cisco Adaptive Security Appliance (ASA) Software
• Cisco Cisco Adaptive Security Appliance (ASA) Software
• Cisco Cisco Adaptive Security Appliance (ASA) Software

Weakness type

• CWE-401

Related vulnerabilities

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• CVE-2026-16028 — Protocol::HTTP2 versions before 1.14 for Perl allow memory exhaustion via closed streams that stream_state never removes from the connection stream table
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