CVE-2021-34753: Cisco Secure Firewall Threat Defense

Medium severity, CVSS 5.3. EPSS: 0.7% chance of exploitation in the next 30 days.

A vulnerability in the payload inspection for Ethernet Industrial Protocol (ENIP) traffic for Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured rules for ENIP traffic. This vulnerability is due to incomplete processing during deep packet inspection for ENIP packets. An attacker could exploit this vulnerability by sending a crafted ENIP packet to the targeted interface. A successful exploit could allow the attacker to bypass configured access control and intrusion policies that should trigger and drop for the ENIP packet.

Affected products

• Cisco Secure Firewall Threat Defense: before 6.4.0.13 (fixed in 6.4.0.13); from 6.5.0, before 6.6.5.1 (fixed in 6.6.5.1); from 6.7.0, before 6.7.0.3 (fixed in 6.7.0.3); version 7.0.0 only

Published 2024-11-15. Last modified 2026-08-11.