CVE-2026-16045 Delegated OAuth tokens could revoke unrelated OAuth application authorizations
Attackers with delegated OAuth tokens can revoke unrelated user authorizations or tokens, bypassing intended access controls in Mattermost.
- 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-2026-16045?
CVE-2026-16045 is a low-severity missing authorization 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 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 Mattermost failed to restrict OAuth deauthorization and personal access token management endpoints to direct user sessions, which allowed an OAuth app with a delegated user token to revoke the user's authorizations or tokens for other integrations via account-management endpoints.. Mattermost Advisory ID: MMSA-2026-00704
Weakness: CWE-863
Which versions are affected by CVE-2026-16045?
It affects 1 product.
Products include Mattermost Mattermost Server.
How do I fix CVE-2026-16045?
Upgrade to a fixed version.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-16045 being exploited?
There is no known exploitation of CVE-2026-16045 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-cgr5-gh7v-f893, MINI-2frp-88gp-95fr, MINI-wrrp-rcxx-2vvr.