Mattermost <10.11.21 & <11.7.6: Undefined Run-State Validation Permits API Modification
CVE-2026-16046 Published on August 17, 2026
Missing run-state validation on finished playbook runs
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to enforce run-state validation on write operations for finished playbook runs which allows a run participant to modify status, checklists, retrospective content, ownership, and participants on completed runs via REST and GraphQL API requests. Mattermost Advisory ID: MMSA-2026-00675
Vulnerability Analysis
CVE-2026-16046 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, with no impact on integrity, and no impact on availability.
Weakness Type
What is an AuthZ Vulnerability?
The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.
CVE-2026-16046 has been classified to as an AuthZ vulnerability or weakness.
Products Associated with CVE-2026-16046
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Affected Versions
Mattermost:- Version 11.7.0, <= 11.7.6 is affected.
- Version 10.11.0, <= 10.11.21 is affected.
- Version 11.9.0 is unaffected.
- Version 11.7.7 is unaffected.
- Version 10.11.22 is unaffected.