CVE-2026-3115

Guest users can view group member IDs without respecting view restrictions

Published Mar 26, 2026 CVSS 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
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

Remediation

Vendor Solution

Update Mattermost to versions 11.5.0, 11.2.3, 10.11.11, 11.4.1, 11.3.2 or higher.

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-mpc7-mm28-f6wq Mattermost allows authenticated guest users to enumerate user IDs outside their allowed visibility scope
References
History
Type Values Removed Values Added
First Time appeared Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:11.4.0:*:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Server
Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
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
Title Guest users can view group member IDs without respecting view restrictions
Weaknesses CWE-863
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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
Mar 26, 2026, 5:51 PM
Reserved
Feb 24, 2026, 11:06 AM
Status
Analyzed
Published
Mar 26, 2026, 5:16 PM
Modified
Jun 17, 2026, 10:43 AM