Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718

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Fixes

Solution

Update Mattermost to versions 11.9.0, 11.7.7, 11.8.4 or higher.


Workaround

No workaround given by the vendor.

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 14:45:00 +0000

Type Values Removed Values Added
Description Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718
Title Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 4.2, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-08-17T15:25:38.145Z

Reserved: 2026-07-14T16:02:49.735Z

Link: CVE-2026-15754

cve-icon Vulnrichment

Updated: 2026-08-17T15:25:33.961Z

cve-icon NVD

Status : Received

Published: 2026-08-17T15:16:53.743

Modified: 2026-08-17T16:16:49.923

Link: CVE-2026-15754

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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

Weaknesses