CVE-2026-16047

Board channel linking without read channel permission validation

State: Published
Severity: 4.3 Medium
Published: Aug 17, 2026
Updated: Aug 17, 2026
Reserved: Jul 17, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N	Mattermost

Weaknesses

CWE-862 Missing Authorization

Affected Products

Product	Versions
MattermostMattermost	11.7.0 through 11.7.6Affected 10.11.0 through 10.11.21Affected 11.8.0 through 11.8.3Affected 11.9.0Not affected 11.7.7Not affected 10.11.22Not affected 11.8.4Not affected

References

MMSA-2026-00674vendor-advisory

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