CVE-2026-3637 — Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13,

title: CVE-2026-3637 - Mattermost Post Edit Without Permission
id: scw-2026-05-18-ai-1
status: experimental
level: medium
description: |
  Detects attempts to modify existing Mattermost posts via the API's POST update endpoint (PUT /api/v4/posts/{post_id}) without proper channel posting permissions, exploiting CVE-2026-3637. This allows authenticated users with revoked posting privileges to alter their posts.
author: SCW Feed Engine (AI-generated)
date: 2026-05-18
references:
  - https://shimiscyberworld.com/posts/nvd-CVE-2026-3637/
tags:
  - attack.privilege_escalation
  - attack.t1078.004
logsource:
    category: webserver
detection:
  selection:
      cs-uri|contains:
          - '/api/v4/posts/'
      cs-method:
          - 'PUT'
      condition: selection
falsepositives:
  - Legitimate administrative activity

Source: Shimi's Cyber World · License & reuse