CVE-2021-34749: Cisco Firepower Management Center Virtual Appliance Firmware

High severity, CVSS 8.6. EPSS: 1.7% chance of exploitation in the next 30 days.

A vulnerability in Server Name Identification (SNI) request filtering of Cisco Web Security Appliance (WSA), Cisco Firepower Threat Defense (FTD), and the Snort detection engine could allow an unauthenticated, remote attacker to bypass filtering technology on an affected device and exfiltrate data from a compromised host. This vulnerability is due to inadequate filtering of the SSL handshake. An attacker could exploit this vulnerability by using data from the SSL client hello packet to communicate with an external server. A successful exploit could allow the attacker to execute a command-and-control attack on a compromised host and perform additional data exfiltration attacks.

Affected products

• Cisco Firepower Management Center Virtual Appliance Firmware: version 6.6.0 only; version 6.7.0 only; version 7.0.0 only; version 7.1.0 only
• Cisco Ironport Web Security Appliance: version 14.5 only
• Cisco Secure Firewall Management Center: version 2.9.18 only

Published 2021-08-18. Last modified 2026-06-17.