---
id: CVE-2026-20067
title: >-
  Multiple Cisco products are affected by a vulnerability in the Snort 3
  detection engine that could allow an unauthenticated, remote attacker to cause
  the Snort 3 Detection Engine to restart, resulting in an interruption of
  packet inspect…
summary: >-
  Multiple Cisco products are affected by a vulnerability in the Snort 3
  detection engine that could allow an unauthenticated, remote attacker to cause
  the Snort 3 Detection Engine to restart, resulting in an interruption of
  packet inspect…
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-787
vendor: cisco
product: snort
affected:
  - 'snort >= 3.0.0-233, < 3.9.5.0'
  - cyber_vision = 3.0.0
  - cyber_vision = 3.0.1
  - cyber_vision = 3.0.2
  - cyber_vision = 3.0.3
  - cyber_vision = 3.0.4
  - cyber_vision = 3.0.5
  - cyber_vision = 3.0.6
  - cyber_vision = 3.1.0
  - cyber_vision = 3.1.1
  - cyber_vision = 3.1.2
  - cyber_vision = 3.2.0
  - cyber_vision = 3.2.1
  - cyber_vision = 3.2.2
  - cyber_vision = 3.2.3
  - cyber_vision = 3.2.4
  - cyber_vision = 4.0.0
  - cyber_vision = 4.0.1
  - cyber_vision = 4.0.2
  - cyber_vision = 4.0.3
  - cyber_vision = 4.1.0
  - cyber_vision = 4.1.1
  - cyber_vision = 4.1.2
  - cyber_vision = 4.1.3
  - cyber_vision = 4.1.4
  - cyber_vision = 4.1.5
  - cyber_vision = 4.1.6
  - cyber_vision = 4.1.7
  - cyber_vision = 4.2.0
  - cyber_vision = 4.2.1
  - cyber_vision = 4.2.2
  - cyber_vision = 4.2.3
  - cyber_vision = 4.2.4
  - cyber_vision = 4.2.6
  - cyber_vision = 4.3.0
  - cyber_vision = 4.3.1
  - cyber_vision = 4.3.2
  - cyber_vision = 4.3.3
  - cyber_vision = 4.4.0
  - cyber_vision = 4.4.1
  - cyber_vision = 4.4.2
  - cyber_vision = 4.4.3
  - cyber_vision = 5.0.0
  - cyber_vision = 5.0.1
  - cyber_vision = 5.0.2
  - cyber_vision = 5.1.0
  - cyber_vision = 5.1.1
  - cyber_vision = 5.1.2
  - cyber_vision = 5.1.3
  - cyber_vision = 5.2.0
  - cyber_vision = 5.2.1
  - cyber_vision = 5.3.0
  - cyber_vision = 5.3.1
  - cyber_vision = 5.3.2
  - secure_firewall_threat_defense = 7.0.0
  - secure_firewall_threat_defense = 7.0.0.1
  - secure_firewall_threat_defense = 7.0.1
  - secure_firewall_threat_defense = 7.0.1.1
  - secure_firewall_threat_defense = 7.0.2
  - secure_firewall_threat_defense = 7.0.2.1
  - secure_firewall_threat_defense = 7.0.3
  - secure_firewall_threat_defense = 7.0.4
  - secure_firewall_threat_defense = 7.0.5
  - secure_firewall_threat_defense = 7.0.6
  - secure_firewall_threat_defense = 7.0.6.1
  - secure_firewall_threat_defense = 7.0.6.2
  - secure_firewall_threat_defense = 7.0.6.3
  - secure_firewall_threat_defense = 7.0.7
  - secure_firewall_threat_defense = 7.0.8
  - secure_firewall_threat_defense = 7.0.8.1
  - secure_firewall_threat_defense = 7.1.0
  - secure_firewall_threat_defense = 7.1.0.1
  - secure_firewall_threat_defense = 7.1.0.2
  - secure_firewall_threat_defense = 7.1.0.3
  - 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
patched:
  - snort 3.9.5.0
published: '2026-03-04'
updated: '2026-08-19'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-20067'
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-multi-dos-XFWkWSwz
    label: psirt@cisco.com
  - url: 'https://software.cisco.com'
tags:
  - nvd
  - csaf
  - vendor-advisory
  - cisco
epss: 0.00482
epssPercentile: 0.4139
ingestedAt: '2026-08-20T17:59:04.357Z'
---

## Overview

Multiple Cisco products are affected by a vulnerability in the Snort 3 detection engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection.&nbsp;

This vulnerability is due to incomplete error checking when parsing the Multicast DNS fields of the HTTP header. An attacker could exploit this vulnerability by sending crafted HTTP packets through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause a DoS condition when the Snort 3 Detection Engine unexpectedly restarts.

## Affected

- `snort >= 3.0.0-233, < 3.9.5.0`
- `cyber_vision = 3.0.0`
- `cyber_vision = 3.0.1`
- `cyber_vision = 3.0.2`
- `cyber_vision = 3.0.3`
- `cyber_vision = 3.0.4`
- `cyber_vision = 3.0.5`
- `cyber_vision = 3.0.6`
- `cyber_vision = 3.1.0`
- `cyber_vision = 3.1.1`
- `cyber_vision = 3.1.2`
- `cyber_vision = 3.2.0`
- `cyber_vision = 3.2.1`
- `cyber_vision = 3.2.2`
- `cyber_vision = 3.2.3`
- `cyber_vision = 3.2.4`
- `cyber_vision = 4.0.0`
- `cyber_vision = 4.0.1`
- `cyber_vision = 4.0.2`
- `cyber_vision = 4.0.3`
- `cyber_vision = 4.1.0`
- `cyber_vision = 4.1.1`
- `cyber_vision = 4.1.2`
- `cyber_vision = 4.1.3`
- `cyber_vision = 4.1.4`
- `cyber_vision = 4.1.5`
- `cyber_vision = 4.1.6`
- `cyber_vision = 4.1.7`
- `cyber_vision = 4.2.0`
- `cyber_vision = 4.2.1`
- `cyber_vision = 4.2.2`
- `cyber_vision = 4.2.3`
- `cyber_vision = 4.2.4`
- `cyber_vision = 4.2.6`
- `cyber_vision = 4.3.0`
- `cyber_vision = 4.3.1`
- `cyber_vision = 4.3.2`
- `cyber_vision = 4.3.3`
- `cyber_vision = 4.4.0`
- `cyber_vision = 4.4.1`
- `cyber_vision = 4.4.2`
- `cyber_vision = 4.4.3`
- `cyber_vision = 5.0.0`
- `cyber_vision = 5.0.1`
- `cyber_vision = 5.0.2`
- `cyber_vision = 5.1.0`
- `cyber_vision = 5.1.1`
- `cyber_vision = 5.1.2`
- `cyber_vision = 5.1.3`
- `cyber_vision = 5.2.0`
- `cyber_vision = 5.2.1`
- `cyber_vision = 5.3.0`
- `cyber_vision = 5.3.1`
- `cyber_vision = 5.3.2`
- `secure_firewall_threat_defense = 7.0.0`
- `secure_firewall_threat_defense = 7.0.0.1`
- `secure_firewall_threat_defense = 7.0.1`
- `secure_firewall_threat_defense = 7.0.1.1`
- `secure_firewall_threat_defense = 7.0.2`
- `secure_firewall_threat_defense = 7.0.2.1`
- `secure_firewall_threat_defense = 7.0.3`
- `secure_firewall_threat_defense = 7.0.4`
- `secure_firewall_threat_defense = 7.0.5`
- `secure_firewall_threat_defense = 7.0.6`
- `secure_firewall_threat_defense = 7.0.6.1`
- `secure_firewall_threat_defense = 7.0.6.2`
- `secure_firewall_threat_defense = 7.0.6.3`
- `secure_firewall_threat_defense = 7.0.7`
- `secure_firewall_threat_defense = 7.0.8`
- `secure_firewall_threat_defense = 7.0.8.1`
- `secure_firewall_threat_defense = 7.1.0`
- `secure_firewall_threat_defense = 7.1.0.1`
- `secure_firewall_threat_defense = 7.1.0.2`
- `secure_firewall_threat_defense = 7.1.0.3`
- `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`

## Remediation

Upgrade past the affected range:

- `snort 3.9.5.0`

## Vendor advisories

- **cisco-sa-snort3-multi-dos-XFWkWSwz** · Cisco · affected: Cisco UTD SNORT IPS Engine Software (44 versions), Cisco Cyber Vision (52 versions), Cisco Firepower 2100 Series, Cisco Firepower 1000 Series, Cisco ASA 5500-X Series Firewalls, Cisco 3000 Series Industrial Security Appliances (ISA), … · updated 2026-03-04 · [advisory](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-multi-dos-XFWkWSwz)