CVE-2026-15754

Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal

State: Published
Severity: 4.2 Medium
Published: Aug 17, 2026
Updated: Aug 17, 2026
Reserved: Jul 14, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	4.2 Medium	CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N	Mattermost

Weaknesses

CWE-863 Incorrect Authorization

Affected Products

Product	Versions
MattermostMattermost	11.7.0 through 11.7.6Affected 11.8.0 through 11.8.3Affected 11.9.0Not affected 11.7.7Not affected 11.8.4Not affected

References

MMSA-2026-00718vendor-advisory

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