CVE-2025-20134: Cisco Adaptive Security Appliance ASA Software

High severity, CVSS 8.6. EPSS: 0.4% chance of exploitation in the next 30 days.

A vulnerability in the certificate processing 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 improper parsing of SSL/TLS certificates. An attacker could exploit this vulnerability by sending crafted DNS packets that match a static Network Address Translation (NAT) rule with DNS inspection enabled through an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Affected products

• Cisco Cisco Adaptive Security Appliance ASA Software: version 9.12.4.39 only; version 9.12.4.40 only; version 9.14.4.6 only; version 9.14.4.7 only; version 9.12.4.41 only; version 9.12.4.47 only; …
• Cisco Cisco Firepower Threat Defense Software: version 6.6.5.2 only; version 6.4.0.15 only; version 6.6.7 only; version 6.4.0.16 only; version 6.6.7.1 only; version 6.4.0.17 only; …

Published 2025-08-14. Last modified 2026-06-17.