CVE-2026-3115

Guest users can view group member IDs without respecting view restrictions

State: Published
Severity: 4.3 Medium
Published: Mar 26, 2026
Updated: Mar 26, 2026
Reserved: Feb 24, 2026

Description

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to apply view restrictions when retrieving group member IDs, which allows authenticated guest users to enumerate user IDs outside their allowed visibility scope via the group retrieval endpoint.. Mattermost Advisory ID: MMSA-2026-00594

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-863 Incorrect Authorization

Affected Products

Product	Versions
MattermostMattermost	11.2.0 through 11.2.2Affected 10.11.0 through 10.11.10Affected 11.4.0 through 11.4.0Affected 11.3.0 through 11.3.1Affected 11.5.0Not affected 11.2.3Not affected 10.11.11Not affected 11.4.1Not affected 11.3.2Not affected

References

MMSA-2026-00594vendor-advisory

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