GHSA-5mr9-crcg-8wh2MediumCVSS 4.3

Mattermost fails to use consistent error responses when handling the /mute command

Published
March 16, 2026
Last Modified
March 18, 2026

🔗 CVE IDs covered (1)

CVE-2026-21386 →

📋 Description

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to use consistent error responses when handling the /mute command which allows an authenticated team member to enumerate private channels they are not authorized to know about via differing error messages for nonexistent versus private channels. Mattermost Advisory ID: MMSA-2026-00588

🎯 Affected products5

  • go/github.com/mattermost/mattermost/server/v8:< 8.0.0-20260130144323-5bb5261c72fa
  • go/github.com/mattermost/mattermost-server:< 5.3.2-0.20260130144323-5bb5261c72fa
  • go/github.com/mattermost/mattermost-server:>= 10.11.0-rc1, < 10.11.11
  • go/github.com/mattermost/mattermost-server:>= 11.2.0-rc1, < 11.2.3
  • go/github.com/mattermost/mattermost-server:>= 11.3.0-rc1, < 11.3.1

🔗 References (4)