GHSA-3vmp-whvv-5v9vMediumCVSS 5.3

Mattermost doesn't validate that a username returned during bot registration belongs to a bot account

Published
June 12, 2026
Last Modified
August 24, 2026

🔗 CVE IDs covered (1)

CVE-2026-6046 →

📋 Description

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username. Mattermost Advisory ID: MMSA-2026-00649

🎯 Affected products4

  • go/github.com/mattermost/mattermost-server:= 11.6.0
  • go/github.com/mattermost/mattermost-server:>= 11.5.0, <= 11.5.4
  • go/github.com/mattermost/mattermost-server:>= 10.11.0, <= 10.11.15
  • go/github.com/mattermost/mattermost/server/v8:>= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260428151657-c79c3831061a

🔗 References (17)