Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Authentication Targeted Denial of Service Vulnerability

Description

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.

Timeline

Scores

EPSS (exploitation in 30 days)

0.80% · top 43% of all CVEs (11 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.6.

Affected products

• Cisco · Cisco Adaptive Security Appliance (ASA) Software

  • affected 9.12.3
  • affected 9.8.3
  • affected 9.12.1
  • affected 9.12.2
  • affected 9.8.2.45
  • affected 9.8.4
  • affected 9.14.1
  • affected 9.12.4
  • affected 9.8.2.35
  • affected 9.8.2.28
  • affected 9.8.2.33
  • affected 9.8.2.38
  • affected 9.8.4.25
  • affected 9.12.3.2
  • affected 9.12.3.7
  • affected 9.8.3.18
  • affected 9.8.3.14
  • affected 9.8.4.15
  • affected 9.8.4.8
  • affected 9.8.3.29
  • affected 9.14.1.10
  • affected 9.12.2.5
  • affected 9.8.4.22
  • affected 9.12.3.12
  • affected 9.8.4.7
  • affected 9.8.4.17
  • affected 9.8.3.16
  • affected 9.8.4.20
  • affected 9.8.3.11
  • affected 9.12.1.3
  • affected 9.8.4.3
  • affected 9.12.2.4
  • affected 9.8.4.12
  • affected 9.12.1.2
  • affected 9.8.3.26
  • affected 9.12.2.9
  • affected 9.12.3.9
  • affected 9.8.3.21
  • affected 9.8.4.10
  • affected 9.12.2.1
  • and 149 more

• Cisco · Cisco Firepower Threat Defense Software

  • affected 6.2.3.14
  • affected 6.4.0.1
  • affected 6.2.3.7
  • affected 6.4.0.2
  • affected 6.2.3.9
  • affected 6.2.3.1
  • affected 6.2.3.2
  • affected 6.4.0.5
  • affected 6.2.3.10
  • affected 6.4.0
  • affected 6.4.0.3
  • affected 6.2.3.6
  • affected 6.4.0.4
  • affected 6.2.3.15
  • affected 6.2.3.5
  • affected 6.2.3.4
  • affected 6.2.3.3
  • affected 6.2.3.8
  • affected 6.4.0.6
  • affected 6.2.3.11
  • affected 6.2.3.12
  • affected 6.2.3.13
  • affected 6.4.0.7
  • affected 6.4.0.8
  • affected 6.6.0
  • affected 6.4.0.9
  • affected 6.2.3.16
  • affected 6.6.0.1
  • affected 6.6.1
  • affected 6.4.0.10
  • affected 6.4.0.11
  • affected 6.6.3
  • affected 6.6.4
  • affected 6.4.0.12
  • affected 7.0.0
  • affected 6.2.3.17
  • affected 7.0.0.1
  • affected 6.6.5
  • affected 7.0.1
  • affected 7.1.0
  • and 47 more

What to do

Exploitation: The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2025-24855 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2025-20133](https://cveledger.app/badge/CVE-2025-20133.svg)](https://cveledger.app/cve/CVE-2025-20133)

Record last updated 14 Aug 2025, 19:21 UTC.