Bug 2451793 (CVE-2026-3115)

Summary: CVE-2026-3115 mattermost: Mattermost: Information disclosure via group retrieval endpoint
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Mattermost. Authenticated guest users can exploit this vulnerability by retrieving group member IDs through the group retrieval endpoint. This failure to apply view restrictions allows them to enumerate user IDs that are outside their permitted visibility scope, leading to information disclosure.
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Description OSIDB Bzimport 2026-03-26 17:03:00 UTC
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