CyberBrief
Subscribe
8.6High

Cisco Secure Firewall Threat Defense

CVE-2021-1402

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.

What this means for your business

  • It affects Cisco Secure Firewall Threat Defense. It matters if your company, or a supplier that handles your data, runs it.
  • An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
  • FIRST's prediction model gives it a 1% chance of attack attempts being seen in the next 30 days, ranking above 70% of all known flaws.

What to do

  1. 1Check whether your company or your suppliers run Cisco Secure Firewall Threat Defense, and which version. The affected versions are listed further down this page.
  2. 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

Check if you’re exposedBook a call

Scoring

CVSS
8.6 (v3.1)
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Weakness
CWE-119
Assigned by
psirt@cisco.com

Dates

Published
2021-04-29
Last modified
2026-08-11
Sources
NVD

Affected products

  • Cisco Secure Firewall Threat Defense6.3.0 - 6.4.0, 6.5.0 - 6.6.0
  • Cisco Firepower Threat Defense Virtualall versions
  • Cisco Asa 5512-Xall versions
  • Cisco Asa 5515-Xall versions
  • Cisco Asa 5525-Xall versions
  • Cisco Asa 5545-Xall versions
  • Cisco Asa 5555-Xall versions
  • Cisco Firepower 1010all versions
  • Cisco Firepower 1120all versions
  • Cisco Firepower 1140all versions
  • Cisco Firepower 1150all versions
  • Cisco Firepower 2110all versions

As listed in the NVD configuration data. Not a statement about your estate.

References