CVE-2026-20006: Cisco Firepower Threat Defense Software and Cisco FirePOWER Services TLS with Snort 3 Denial of Service Vulnerability

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.