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
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-3vmp-whvv-5v9v Mattermost doesn't validate that a username returned during bot registration belongs to a bot account
Fixes

Solution

Update Mattermost to versions 11.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17 or higher.


Workaround

No workaround given by the vendor.

References
History

Fri, 12 Jun 2026 18:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Fri, 12 Jun 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 12 Jun 2026 17:15:00 +0000

Type Values Removed Values Added
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
Title Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server
Weaknesses CWE-200
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-06-12T17:18:30.553Z

Reserved: 2026-04-09T19:20:26.868Z

Link: CVE-2026-6046

cve-icon Vulnrichment

Updated: 2026-06-12T17:18:27.704Z

cve-icon NVD

Status : Analyzed

Published: 2026-06-12T17:16:26.957

Modified: 2026-06-18T14:33:35.203

Link: CVE-2026-6046

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-12T19:00:21Z

Weaknesses