Secure Firewall ASA and FTD
CVE-2025-20134: Cisco Adaptive Security Appliance and Firepower Threat Defense Software SSL/TLS Certificate Denial of Service Vulnerability
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.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.12 | See the advisory |
| Cisco Adaptive Security Appliance (ASA) Software 9.14 | See the advisory |
| Cisco Firepower Threat Defense Software 6.6 | See the advisory |
| Cisco Firepower Threat Defense Software 6.4 | See the advisory |
| Cisco Firepower Threat Defense Software 6.6 | See the advisory |
| Cisco Firepower Threat Defense Software 6.4 | See the advisory |
| Cisco Firepower Threat Defense Software 6.6 | See the advisory |
| Cisco Firepower Threat Defense Software 6.4 | See the advisory |
| Cisco Firepower Threat Defense Software 6.6 | See the advisory |
| Cisco Firepower Threat Defense Software 6.4 | See the advisory |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
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.
Exploitation
The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 11 Oct 2026.