Mattermost 11.7.6 Guest Escalation to Board Admin via .boardarchive
CVE-2026-16044 Published on August 17, 2026
Insufficient validation of guest board admin privileges on archive import
Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID: MMSA-2026-00672
Vulnerability Analysis
CVE-2026-16044 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 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-2026-16044 has been classified to as an AuthZ vulnerability or weakness.
Products Associated with CVE-2026-16044
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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.