Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674
References
History

Mon, 17 Aug 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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


Mon, 17 Aug 2026 15:45:00 +0000

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

Mon, 17 Aug 2026 14:30:00 +0000

Type Values Removed Values Added
Description Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674
Title Board channel linking without read channel permission validation
Weaknesses CWE-862
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-08-17T15:26:34.376Z

Reserved: 2026-07-17T09:44:04.187Z

Link: CVE-2026-16047

cve-icon Vulnrichment

Updated: 2026-08-17T15:26:27.165Z

cve-icon NVD

Status : Received

Published: 2026-08-17T15:16:54.193

Modified: 2026-08-17T16:16:50.657

Link: CVE-2026-16047

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T15:45:03Z