---
id: CVE-2026-86349
title: >-
  Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.8,
  10.11.x <= 10.11.22 fail to limit the nesting depth in the server-side
  Markdown parser which allows an authenticated attacker to cause a denial of
  service (CPU res…
summary: >-
  Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.8,
  10.11.x <= 10.11.22 fail to limit the nesting depth in the server-side
  Markdown parser which allows an authenticated attacker to cause a denial of
  service (CPU res…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-407
vendor: Mattermost
product: Mattermost
affected:
  - Mattermost >= 11.9.0 <= 11.9.0
  - Mattermost >= 11.8.0 <= 11.8.4
  - Mattermost >= 11.7.0 <= 11.7.8
  - Mattermost >= 10.11.0 <= 10.11.22
published: '2026-09-14'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T19:30:49.967'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86349'
references:
  - url: 'https://mattermost.com/security-updates'
    label: responsibledisclosure@mattermost.com
tags:
  - nvd
  - cve.org
epss: 0.00359
epssPercentile: 0.26922
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-14T19:13:43.392628Z'
ingestedAt: '2026-09-14T15:23:07.422Z'
---

## Overview

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.8, 10.11.x <= 10.11.22 fail to limit the nesting depth in the server-side Markdown parser which allows an authenticated attacker to cause a denial of service (CPU resource exhaustion) via a crafted post containing deeply nested blockquotes or list items.. Mattermost Advisory ID: MMSA-2026-00707

## Remediation

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