---
id: CVE-2026-20011
title: Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability
summary: "Multiple Cisco products are affected by a vulnerability in the Snort 3 SMTP MIME Decoder that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart.\r\n\r\nThis vulnerability is due to a lack of err…"
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'
cvssSource: cna
cwe:
  - CWE-805
vendor: Cisco
product: Cisco Open Source Snort3
affected:
  - open_source_snort3 3.1.2.0
  - open_source_snort3 3.1.3.0
  - open_source_snort3 3.1.4.0
  - open_source_snort3 3.1.5.0
  - open_source_snort3 3.1.6.0
  - open_source_snort3 3.1.7.0
  - open_source_snort3 3.1.8.0
  - open_source_snort3 3.1.9.0
  - open_source_snort3 3.1.10.0
  - open_source_snort3 3.1.12.0
  - open_source_snort3 3.1.13.0
  - open_source_snort3 3.1.14.0
  - open_source_snort3 3.1.15.0
  - open_source_snort3 3.1.16.0
  - open_source_snort3 3.1.17.0
  - open_source_snort3 3.1.18.0
  - open_source_snort3 3.1.19.0
  - open_source_snort3 3.1.20.0
  - open_source_snort3 3.1.21.0
  - open_source_snort3 3.1.22.0
  - open_source_snort3 3.1.23.0
  - open_source_snort3 3.1.24.0
  - open_source_snort3 3.1.25.0
  - open_source_snort3 3.1.27.0
  - open_source_snort3 3.1.28.0
  - open_source_snort3 3.1.29.0
  - open_source_snort3 3.1.30.0
  - open_source_snort3 3.1.31.0
  - open_source_snort3 3.1.32.0
  - open_source_snort3 3.1.36.0
  - open_source_snort3 3.1.38.0
  - open_source_snort3 3.1.39.0
  - open_source_snort3 3.1.40.0
  - open_source_snort3 3.1.41.0
  - open_source_snort3 3.1.42.0
  - open_source_snort3 3.1.43.0
  - open_source_snort3 3.1.45.0
  - open_source_snort3 3.1.47.0
  - open_source_snort3 3.1.48.0
  - open_source_snort3 3.1.50.0
  - open_source_snort3 3.1.51.0
  - open_source_snort3 3.1.52.0
  - open_source_snort3 3.1.53.0
  - open_source_snort3 3.1.55.0
  - open_source_snort3 3.1.56.0
  - open_source_snort3 3.1.57.0
  - open_source_snort3 3.1.58.0
  - open_source_snort3 3.1.59.0
  - open_source_snort3 3.1.60.0
  - open_source_snort3 3.1.61.0
published: '2026-10-21'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T16:12:19.429Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-20011'
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-mime-vulns-bkXjcKkt
    label: cisco-sa-snort3-mime-vulns-bkXjcKkt
tags:
  - cve.org
ingestedAt: '2026-10-21T17:07:51.309Z'
---

## Overview

Multiple Cisco products are affected by a vulnerability in the Snort 3 SMTP MIME Decoder that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart.

This vulnerability is due to a lack of error checking when the MIME fields of the SMTP header are parsed. An attacker could exploit this vulnerability by sending crafted SMTP packets through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when the Snort 3 Detection Engine unexpectedly restarts.

## Affected

- `open_source_snort3 3.1.2.0`
- `open_source_snort3 3.1.3.0`
- `open_source_snort3 3.1.4.0`
- `open_source_snort3 3.1.5.0`
- `open_source_snort3 3.1.6.0`
- `open_source_snort3 3.1.7.0`
- `open_source_snort3 3.1.8.0`
- `open_source_snort3 3.1.9.0`
- `open_source_snort3 3.1.10.0`
- `open_source_snort3 3.1.12.0`
- `open_source_snort3 3.1.13.0`
- `open_source_snort3 3.1.14.0`
- `open_source_snort3 3.1.15.0`
- `open_source_snort3 3.1.16.0`
- `open_source_snort3 3.1.17.0`
- `open_source_snort3 3.1.18.0`
- `open_source_snort3 3.1.19.0`
- `open_source_snort3 3.1.20.0`
- `open_source_snort3 3.1.21.0`
- `open_source_snort3 3.1.22.0`
- `open_source_snort3 3.1.23.0`
- `open_source_snort3 3.1.24.0`
- `open_source_snort3 3.1.25.0`
- `open_source_snort3 3.1.27.0`
- `open_source_snort3 3.1.28.0`
- `open_source_snort3 3.1.29.0`
- `open_source_snort3 3.1.30.0`
- `open_source_snort3 3.1.31.0`
- `open_source_snort3 3.1.32.0`
- `open_source_snort3 3.1.36.0`
- `open_source_snort3 3.1.38.0`
- `open_source_snort3 3.1.39.0`
- `open_source_snort3 3.1.40.0`
- `open_source_snort3 3.1.41.0`
- `open_source_snort3 3.1.42.0`
- `open_source_snort3 3.1.43.0`
- `open_source_snort3 3.1.45.0`
- `open_source_snort3 3.1.47.0`
- `open_source_snort3 3.1.48.0`
- `open_source_snort3 3.1.50.0`
- `open_source_snort3 3.1.51.0`
- `open_source_snort3 3.1.52.0`
- `open_source_snort3 3.1.53.0`
- `open_source_snort3 3.1.55.0`
- `open_source_snort3 3.1.56.0`
- `open_source_snort3 3.1.57.0`
- `open_source_snort3 3.1.58.0`
- `open_source_snort3 3.1.59.0`
- `open_source_snort3 3.1.60.0`
- `open_source_snort3 3.1.61.0`

## Remediation

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