CVE-2026-16048 Channel member roles accept out-of-scope roles
A channel administrator can gain additional channel permissions by assigning out-of-scope roles via the API, leading to privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-16048?
CVE-2026-16048 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 17 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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
Weakness: CWE-863
Which versions are affected by CVE-2026-16048?
It affects 1 product.
Products include Mattermost Mattermost Server.
How do I fix CVE-2026-16048?
Upgrade to a fixed version.
Is CVE-2026-16048 being exploited?
There is no known exploitation of CVE-2026-16048 in the wild and no public exploit code.
Other vulnerabilities in Mattermost Mattermost Server
- CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers
- CVE-2025-12421 Account Takeover via Code Exchange Endpoint
- CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User
- CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards
- CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive
Sources
Also known as GHSA-v37p-g38w-w7wg, MINI-68ff-8vr7-h3vp, MINI-hxw7-fm32-g34c.