CVE-2026-20249
Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software IKEv2 Certificate Authentication Denial of Service Vulnerability
Description
A vulnerability in the certification authentication feature of Internet Key Exchange version 2 (IKEv2) for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly. This vulnerability is due to a logic error during the certificate authentication phase of the IKEv2 connection setup. An attacker could exploit this vulnerability by attempting to establish an IKEv2 VPN connection with a crafted certificate. A successful exploit could allow the attacker to cause the IKEv2 process to crash, causing a denial of service (DoS) condition.
Weakness: CWE-704
Affected products
| Vendor | Product | Category | Matched by |
|---|---|---|---|
| Cisco | Cisco Adaptive Security Appliance (ASA) Check your version | Firewall / NGFW | cna-assigner |
| Cisco | Cisco Firepower Threat Defense (FTD) Check your version | Firewall / NGFW | cna-assigner |
Vendor-reported products (2)
- Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- Cisco · Cisco Secure Firewall Threat Defense (FTD) Software
Vendor advisory
cisco-sa-asaftd-ikev2cert-dos-uWyc2xtv
Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software IKEv2 Certificate Authentication Denial of Service Vulnerability
Cisco’s rating: High (advisory CVSS 8.6) · Published Sep 16, 2026 · updated Sep 18, 2026 (revision 1.1)
Bug ID: CSCwt42671
The vendor’s rating applies to the whole advisory and can differ from this CVE’s own CVSS severity. Where this comes from