CVE-2019-1691: Cisco Secure Firewall Threat Defense

Medium severity, CVSS 5.8. EPSS: 2.3% chance of exploitation in the next 30 days.

A vulnerability in the detection engine of Cisco Firepower Threat Defense Software could allow an unauthenticated, remote attacker to cause the unexpected restart of the SNORT detection engine, resulting in a denial of service (DoS) condition. The vulnerability is due to the incomplete error handling of the SSL or TLS packet header during the connection establishment. An attacker could exploit this vulnerability by sending a crafted SSL or TLS packet during the connection handshake. An exploit could allow the attacker to cause the SNORT detection engine to unexpectedly restart, resulting in a partial DoS condition while the detection engine restarts. Versions prior to 6.2.3.4 are affected.

Affected products

• Cisco Secure Firewall Threat Defense: before 6.2.3.4 (fixed in 6.2.3.4)

Published 2019-02-21. Last modified 2026-08-11.