---
id: CVE-2026-20006
title: >-
  A vulnerability in the TLS cryptography functionality of the Snort 3 Detection
  Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an
  unauthenticated, remote attacker to cause the Snort 3 Detection Engine to
  unexpec…
summary: >-
  A vulnerability in the TLS cryptography functionality of the Snort 3 Detection
  Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an
  unauthenticated, remote attacker to cause the Snort 3 Detection Engine to
  unexpec…
severity: medium
cvss: 5.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L'
cwe:
  - CWE-388
vendor: cisco
product: secure_firewall_threat_defense
affected:
  - secure_firewall_threat_defense = 7.2.0
  - secure_firewall_threat_defense = 7.2.0.1
  - secure_firewall_threat_defense = 7.2.1
  - secure_firewall_threat_defense = 7.2.2
  - secure_firewall_threat_defense = 7.2.3
  - secure_firewall_threat_defense = 7.2.4
  - secure_firewall_threat_defense = 7.2.4.1
  - secure_firewall_threat_defense = 7.2.5
  - secure_firewall_threat_defense = 7.2.5.1
  - secure_firewall_threat_defense = 7.2.5.2
  - secure_firewall_threat_defense = 7.2.6
  - secure_firewall_threat_defense = 7.2.7
  - secure_firewall_threat_defense = 7.2.8
  - secure_firewall_threat_defense = 7.2.8.1
  - secure_firewall_threat_defense = 7.2.9
  - secure_firewall_threat_defense = 7.2.10
  - secure_firewall_threat_defense = 7.2.10.2
  - secure_firewall_threat_defense = 7.3.0
  - secure_firewall_threat_defense = 7.3.1
  - secure_firewall_threat_defense = 7.3.1.1
  - secure_firewall_threat_defense = 7.3.1.2
  - secure_firewall_threat_defense = 7.4.0
  - secure_firewall_threat_defense = 7.4.1
  - secure_firewall_threat_defense = 7.4.1.1
  - secure_firewall_threat_defense = 7.4.2
  - secure_firewall_threat_defense = 7.4.2.1
  - secure_firewall_threat_defense = 7.4.2.2
  - secure_firewall_threat_defense = 7.4.2.3
  - secure_firewall_threat_defense = 7.4.2.4
  - secure_firewall_threat_defense = 7.6.0
  - secure_firewall_threat_defense = 7.6.1
  - secure_firewall_threat_defense = 7.6.2
  - secure_firewall_threat_defense = 7.6.2.1
published: '2026-03-04'
updated: '2026-08-20'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-20006'
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tcp-dos-rHfqnwRg
    label: psirt@cisco.com
tags:
  - nvd
epss: 0.00373
epssPercentile: 0.3107
ingestedAt: '2026-08-20T17:59:03.999Z'
---

## Overview

A vulnerability in the TLS cryptography functionality of the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to unexpectedly restart, resulting in a denial of service (DoS) condition.

This vulnerability is due to improper implementation of the TLS protocol. An attacker could exploit this vulnerability by sending a crafted TLS packet to an affected system. A successful exploit could allow the attacker to cause a device that is running Cisco Secure FTD Software to drop network traffic, resulting in a DoS condition. 
Note: TLS 1.3 is not affected by this vulnerability.

## Affected

- `secure_firewall_threat_defense = 7.2.0`
- `secure_firewall_threat_defense = 7.2.0.1`
- `secure_firewall_threat_defense = 7.2.1`
- `secure_firewall_threat_defense = 7.2.2`
- `secure_firewall_threat_defense = 7.2.3`
- `secure_firewall_threat_defense = 7.2.4`
- `secure_firewall_threat_defense = 7.2.4.1`
- `secure_firewall_threat_defense = 7.2.5`
- `secure_firewall_threat_defense = 7.2.5.1`
- `secure_firewall_threat_defense = 7.2.5.2`
- `secure_firewall_threat_defense = 7.2.6`
- `secure_firewall_threat_defense = 7.2.7`
- `secure_firewall_threat_defense = 7.2.8`
- `secure_firewall_threat_defense = 7.2.8.1`
- `secure_firewall_threat_defense = 7.2.9`
- `secure_firewall_threat_defense = 7.2.10`
- `secure_firewall_threat_defense = 7.2.10.2`
- `secure_firewall_threat_defense = 7.3.0`
- `secure_firewall_threat_defense = 7.3.1`
- `secure_firewall_threat_defense = 7.3.1.1`
- `secure_firewall_threat_defense = 7.3.1.2`
- `secure_firewall_threat_defense = 7.4.0`
- `secure_firewall_threat_defense = 7.4.1`
- `secure_firewall_threat_defense = 7.4.1.1`
- `secure_firewall_threat_defense = 7.4.2`
- `secure_firewall_threat_defense = 7.4.2.1`
- `secure_firewall_threat_defense = 7.4.2.2`
- `secure_firewall_threat_defense = 7.4.2.3`
- `secure_firewall_threat_defense = 7.4.2.4`
- `secure_firewall_threat_defense = 7.6.0`
- `secure_firewall_threat_defense = 7.6.1`
- `secure_firewall_threat_defense = 7.6.2`
- `secure_firewall_threat_defense = 7.6.2.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.