CVE-2026-10527
Received Received - Intake

Privilege Escalation in Mattermost Boards

Publication date: 2026-08-17

Last updated on: 2026-08-17

Assigner: Mattermost, Inc.

Description
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fails to reconcile SchemeAdmin flags with a user's current role which allows a user demoted to System Guest to retain Board Admin privileges and perform admin-only operations via the Boards REST API or UI.. Mattermost Advisory ID: MMSA-2026-00691

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Meta Information

Published
2026-08-17
Last Modified
2026-08-17
Generated
2026-08-17
AI Q&A
2026-08-17
EPSS Evaluated
N/A
NVD
CVE-2026-10527
EUVD
EUVD-2026-60192

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
mattermost mattermost to 11.7.6 (inc)
mattermost mattermost to 10.11.21 (inc)
mattermost mattermost to 11.8.3 (inc)

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

Mattermost versions between 11.7.0 and 11.7.6, 10.11.0 and 10.11.21, and 11.8.0 and 11.8.3 have a flaw where demoting a user to System Guest does not remove their Board Admin privileges. This allows them to perform admin-only operations via the Boards REST API or UI despite their role change.

Detection Guidance

This vulnerability can be detected by checking user roles and privileges in Mattermost, particularly for users who were demoted from Board Admin to System Guest. Review user permissions via the Boards REST API or UI to identify retained admin privileges. Ensure Mattermost versions are updated beyond the affected ranges (11.7.6, 10.11.21, 11.8.3).

Impact Analysis

An attacker with a demoted account could retain unauthorized access to sensitive admin functions, potentially leading to data breaches, unauthorized modifications, or other malicious activities within the Mattermost Boards system.

Compliance Impact

This vulnerability could lead to unauthorized access to personal or sensitive data, violating GDPR's data protection principles or HIPAA's access control requirements. Organizations using affected versions may face compliance violations and potential penalties.

Mitigation Strategies

Update Mattermost to a patched version (11.7.7 or later, 10.11.22 or later, 11.8.4 or later) to resolve the privilege escalation issue.

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