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… (CVE-2026-10527)
Mattermost versions 11.7.x up to 11.7.6, 10.11.x up to 10.11.21, and 11.8.x up to 11.8.3 contain a vulnerability where the system fails to properly reconcile SchemeAdmin flags with a user's current role. This flaw allows users who have been demoted to System Guest to retain Board Admin privileges and perform administrative actions through the Boards REST API or UI.
AI Analysis
Technical Summary
The vulnerability identified as CVE-2026-10527 affects Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, and 11.8.x <= 11.8.3. It arises from a failure to reconcile SchemeAdmin flags with a user's current role, enabling a user demoted to System Guest to retain Board Admin privileges. This allows unauthorized execution of admin-only operations via the Boards REST API or UI. The issue is classified under CWE-863 (Incorrect Authorization). The CVSS 3.1 base score is 6.3, indicating a medium severity vulnerability with network attack vector, low attack complexity, requiring low privileges and no user interaction, impacting confidentiality, integrity, and availability.
Potential Impact
An attacker who has been demoted to the System Guest role can still perform administrative actions on Boards, potentially leading to unauthorized access and modification of board data. This undermines role-based access controls and could result in partial compromise of confidentiality, integrity, and availability of the affected Mattermost Boards functionality.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory (Mattermost Advisory ID: MMSA-2026-00691) for current remediation guidance. Until an official fix is available, restrict access to the Boards REST API and UI to trusted users and monitor for unusual administrative activity related to board management.
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… (CVE-2026-10527)
Description
Mattermost versions 11.7.x up to 11.7.6, 10.11.x up to 10.11.21, and 11.8.x up to 11.8.3 contain a vulnerability where the system fails to properly reconcile SchemeAdmin flags with a user's current role. This flaw allows users who have been demoted to System Guest to retain Board Admin privileges and perform administrative actions through the Boards REST API or UI.
CVSS v3.1
Score 6.3medium
Affected software
pkg:github/mattermost/mattermost-serverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability identified as CVE-2026-10527 affects Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, and 11.8.x <= 11.8.3. It arises from a failure to reconcile SchemeAdmin flags with a user's current role, enabling a user demoted to System Guest to retain Board Admin privileges. This allows unauthorized execution of admin-only operations via the Boards REST API or UI. The issue is classified under CWE-863 (Incorrect Authorization). The CVSS 3.1 base score is 6.3, indicating a medium severity vulnerability with network attack vector, low attack complexity, requiring low privileges and no user interaction, impacting confidentiality, integrity, and availability.
Potential Impact
An attacker who has been demoted to the System Guest role can still perform administrative actions on Boards, potentially leading to unauthorized access and modification of board data. This undermines role-based access controls and could result in partial compromise of confidentiality, integrity, and availability of the affected Mattermost Boards functionality.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory (Mattermost Advisory ID: MMSA-2026-00691) for current remediation guidance. Until an official fix is available, restrict access to the Boards REST API and UI to trusted users and monitor for unusual administrative activity related to board management.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-ghq9-4rcg-jvc2
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-10527"]
- Ecosystems
- []
- Database Specific Severity
- MODERATE
- Cvss Version
- 3.1
Threat ID: 6a833342bf8831d5392a3a9f
Added to database: 08/17/2026, 16:13:54 UTC
Last enriched: 08/17/2026, 16:15:58 UTC
Last updated: 08/17/2026, 19:01:19 UTC
Views: 3
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