CVE-2026-3115
Received Received - Intake
Authorization Bypass in Mattermost Group Member ID Retrieval

Publication date: 2026-03-26

Last updated on: 2026-03-30

Assigner: Mattermost, Inc.

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
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Meta Information
Published
2026-03-26
Last Modified
2026-03-30
Generated
2026-06-16
AI Q&A
2026-03-26
EPSS Evaluated
2026-06-14
NVD
CVE-2026-3115
EUVD
EUVD-2026-16245
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
mattermost mattermost_server From 10.11.0 (inc) to 10.11.11 (exc)
mattermost mattermost_server From 11.2.0 (inc) to 11.2.3 (exc)
mattermost mattermost_server From 11.3.0 (inc) to 11.3.2 (exc)
mattermost mattermost_server 11.4.0
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-863 The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
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Executive Summary

This vulnerability affects certain versions of Mattermost where the system fails to properly enforce view restrictions when retrieving group member IDs. As a result, authenticated guest users can access and enumerate user IDs that are outside their permitted visibility scope by exploiting the group retrieval endpoint.

Impact Analysis

The impact of this vulnerability is that unauthorized users, specifically authenticated guest users, can gain access to user ID information that they should not be able to see. This could lead to privacy concerns and potential information disclosure within the affected Mattermost environment.

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