CVE-2026-20006: Cisco Secure Firewall Threat Defense

Medium severity, CVSS 5.8. EPSS: 0.4% chance of exploitation in the next 30 days.

A vulnerability in the TLS cryptography functionality of the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to unexpectedly restart, resulting in a denial of service (DoS) condition. This vulnerability is due to improper implementation of the TLS protocol. An attacker could exploit this vulnerability by sending a crafted TLS packet to an affected system. A successful exploit could allow the attacker to cause a device that is running Cisco Secure FTD Software to drop network traffic, resulting in a DoS condition.  Note: TLS 1.3 is not affected by this vulnerability.

Affected products

• Cisco Secure Firewall Threat Defense: version 7.2.0 only; version 7.2.0.1 only; version 7.2.1 only; version 7.2.2 only; version 7.2.3 only; version 7.2.4 only; …

Published 2026-03-04. Last modified 2026-08-20.