CVE-2019-1691: Cisco Firepower Threat Defense Software SSL or TLS Denial of Service Vulnerability

Severity: medium (CVSS 5.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2019-02-21 · updated 2026-08-11
Weakness: CWE-20

Description

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 Firepower Threat Defense Software: before 6.2.3.4 — fixed in 6.2.3.4

How to fix

Upgrade to a fixed version: Cisco Firepower Threat Defense Software 6.2.3.4. Check the vendor advisory for mitigations.

References

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