---
id: CVE-2026-20290
title: "A vulnerability in SSL/TLS certificate parsing in the Snort 2 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 2 Detection Engine to restart.\r\n\r\nTh…"
summary: "A vulnerability in SSL/TLS certificate parsing in the Snort 2 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 2 Detection Engine to restart.\r\n\r\nTh…"
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-805
vendor: Cisco
product: Cisco Secure Firewall Threat Defense (FTD) Software
affected:
  - secure_firewall_threat_defense_ftd_software 7.0.0
  - secure_firewall_threat_defense_ftd_software 7.0.0.1
  - secure_firewall_threat_defense_ftd_software 7.0.1
  - secure_firewall_threat_defense_ftd_software 7.0.1.1
  - secure_firewall_threat_defense_ftd_software 7.0.2
  - secure_firewall_threat_defense_ftd_software 7.2.0
  - secure_firewall_threat_defense_ftd_software 7.0.2.1
  - secure_firewall_threat_defense_ftd_software 7.0.3
  - secure_firewall_threat_defense_ftd_software 7.2.0.1
  - secure_firewall_threat_defense_ftd_software 7.0.4
  - secure_firewall_threat_defense_ftd_software 7.2.1
  - secure_firewall_threat_defense_ftd_software 7.0.5
  - secure_firewall_threat_defense_ftd_software 7.3.0
  - secure_firewall_threat_defense_ftd_software 7.2.2
  - secure_firewall_threat_defense_ftd_software 7.2.3
  - secure_firewall_threat_defense_ftd_software 7.3.1
  - secure_firewall_threat_defense_ftd_software 7.2.4
  - secure_firewall_threat_defense_ftd_software 7.0.6
  - secure_firewall_threat_defense_ftd_software 7.2.5
  - secure_firewall_threat_defense_ftd_software 7.2.4.1
  - secure_firewall_threat_defense_ftd_software 7.3.1.1
  - secure_firewall_threat_defense_ftd_software 7.4.0
  - secure_firewall_threat_defense_ftd_software 7.0.6.1
  - secure_firewall_threat_defense_ftd_software 7.2.5.1
  - secure_firewall_threat_defense_ftd_software 7.4.1
  - secure_firewall_threat_defense_ftd_software 7.2.6
  - secure_firewall_threat_defense_ftd_software 7.0.6.2
  - secure_firewall_threat_defense_ftd_software 7.4.1.1
  - secure_firewall_threat_defense_ftd_software 7.2.7
  - secure_firewall_threat_defense_ftd_software 7.2.5.2
  - secure_firewall_threat_defense_ftd_software 7.3.1.2
  - secure_firewall_threat_defense_ftd_software 7.2.8
  - secure_firewall_threat_defense_ftd_software 7.6.0
  - secure_firewall_threat_defense_ftd_software 7.4.2
  - secure_firewall_threat_defense_ftd_software 7.2.8.1
  - secure_firewall_threat_defense_ftd_software 7.0.6.3
  - secure_firewall_threat_defense_ftd_software 7.4.2.1
  - secure_firewall_threat_defense_ftd_software 7.2.9
  - secure_firewall_threat_defense_ftd_software 7.0.7
  - secure_firewall_threat_defense_ftd_software 7.4.2.2
  - secure_firewall_threat_defense_ftd_software 7.2.10
  - secure_firewall_threat_defense_ftd_software 7.6.1
  - secure_firewall_threat_defense_ftd_software 7.4.2.3
  - secure_firewall_threat_defense_ftd_software 7.0.8
  - secure_firewall_threat_defense_ftd_software 7.6.2
  - secure_firewall_threat_defense_ftd_software 7.0.8.1
  - secure_firewall_threat_defense_ftd_software 7.6.2.1
  - secure_firewall_threat_defense_ftd_software 7.4.2.4
  - secure_firewall_threat_defense_ftd_software 7.2.10.2
  - secure_firewall_threat_defense_ftd_software 7.4.3
published: '2026-09-16'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T13:28:28.567'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-20290'
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snort2-ssldos-Mw7WYX9c
    label: psirt@cisco.com
  - url: 'https://software.cisco.com'
tags:
  - nvd
  - cve.org
  - csaf
  - vendor-advisory
  - cisco
epss: 0.0019
epssPercentile: 0.07647
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-17T17:25:32.306457Z'
ingestedAt: '2026-09-16T16:37:52.173Z'
---

## Overview

A vulnerability in SSL/TLS certificate parsing in the Snort 2 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 2 Detection Engine to restart.

This vulnerability is due to incomplete validation of the SSL certificate. An attacker could exploit this vulnerability by sending a crafted SSL connection setup request to be parsed by Snort 2. A successful exploit could allow the attacker to cause the Snort 2 Detection Engine to restart unexpectedly, resulting in a denial of service (DoS) condition.

## Remediation

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

## Vendor advisories

- **cisco-sa-ftd-snort2-ssldos-Mw7WYX9c** · Cisco · affected: Cisco Firepower 2100 Series, Cisco Firepower 1000 Series, Cisco ASA 5500-X Series Firewalls, Cisco 3000 Series Industrial Security Appliances (ISA), Cisco Firepower 9000 Series, Cisco Firepower 4100 Series, … · updated 2026-09-16 · [advisory](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snort2-ssldos-Mw7WYX9c)