CVE-2021-1402

Cisco Firepower Threat Defense Software SSL Decryption Policy Denial of Service Vulnerability

HIGH

8.6

CVSS Score

Published: April 29, 2021 at 05:15 PM UTC

Updated: August 11, 2026 at 07:33 PM UTC

16 products affected across 1 vendorSecure Firewall Threat DefenseAsa 5525-XAsa 5555-X

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Severity

HIGH8.6

Exploit prediction

EPSS 1%

SSVC

No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Secure Firewall Threat Defense · Cisco

95%

6.3.0 ≤ v < 6.4.06.5.0 ≤ v < 6.6.0

cisco-asa-5512-x (environment) · cisco-asa-5515-x (environment) · cisco-asa-5525-x (environment) · cisco-asa-5545-x (environment) · cisco-asa-5555-x (environment) · cisco-firepower-1010 (environment) · cisco-firepower-1120 (environment) · cisco-firepower-1140 (environment) · cisco-firepower-1150 (environment) · cisco-firepower-2110 (environment) · cisco-firepower-2120 (environment) · cisco-firepower-2130 (environment) · cisco-firepower-2140 (environment) · cisco-firepower-threat-defense-virtual (environment) · cisco-isa-3000 (environment)

Asa 5512-X · Ciscodevice

80%

All versions

Asa 5515-X · Ciscodevice

80%

All versions

Asa 5525-X · Ciscodevice

80%

All versions

Asa 5545-X · Ciscodevice

80%

All versions