Mattermost Channel Role Assignment Bypass via API (v10.11-11.8)
CVE-2026-16048 Published on August 17, 2026
Channel member roles accept out-of-scope roles
Mattermost versions 11.8.x <= 11.8.2, 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to restrict channel member role assignment to channel-scoped roles which allows a channel administrator to gain additional channel permissions via the channel member roles API.. Mattermost Advisory ID: MMSA-2026-00697
Vulnerability Analysis
CVE-2026-16048 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 be low. considered to have a small impact on confidentiality and 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-2026-16048 has been classified to as an AuthZ vulnerability or weakness.
Products Associated with CVE-2026-16048
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Affected Versions
Mattermost:- Version 11.8.0, <= 11.8.2 is affected.
- 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 11.8.3 is unaffected.
- Version 11.7.7 is unaffected.
- Version 10.11.22 is unaffected.