GitHub Advisoryadvisory · Go

GHSA-3vmp-whvv-5v9v Mattermost doesn't validate that a username returned during bot registration belongs to a bot account

MEDIUM Published 2026-06-12 Modified 2026-08-24 Official page ↗
Aliases
CVE-2026-6046
Ecosystem
Go
Packages
github.com/mattermost/mattermost-server, github.com/mattermost/mattermost/server/v8
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Weaknesses
CWE-200
Reviewed
2026-08-24

Affected packages

• Go github.com/mattermost/mattermost-server: >= 11.6.0, < 11.6.1 → fixed in 11.6.1 • Go github.com/mattermost/mattermost-server: >= 11.5.0, < 11.5.5 → fixed in 11.5.5 • Go github.com/mattermost/mattermost-server: >= 10.11.0, < 10.11.17 → fixed in 10.11.17 • Go github.com/mattermost/mattermost/server/v8: >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260428151657-c79c3831061a → fixed in 8.0.0-20260428151657-c79c3831061a

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

Related

Alias · CVE (1)

  • CVE-2026-6046 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… vulnerability

Weakness · CWE (1)

  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor weakness

References