CVE-2021-1402: Cisco Firepower Threat Defense Software SSL Decryption Policy Denial of Service Vulnerability

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-04-29 · updated 2026-08-11
Weakness: CWE-119

Description

A vulnerability in the software-based SSL/TLS message handler of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient validation of SSL/TLS messages when the device performs software-based SSL decryption. An attacker could exploit this vulnerability by sending a crafted SSL/TLS message through an affected device. SSL/TLS messages sent to an affected device do not trigger this vulnerability. A successful exploit could allow the attacker to cause a process to crash. This crash would then trigger a reload of the device. No manual intervention is needed to recover the device after the reload.

Affected products

Cisco Firepower Threat Defense Software: from 6.3.0 before 6.4.0; from 6.5.0 before 6.6.0 — fixed in 6.4.0, 6.6.0

How to fix

Upgrade to a fixed version: Cisco Firepower Threat Defense Software 6.4.0, 6.6.0. Check the vendor advisory for mitigations.

References

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