CVE-2025-27715 Auto-Enrollment of Team Admins into Private Channels without explicit consent
Team admins can be added to private channels without consent via crafted links, bypassing authorization checks in Mattermost.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-27715?
CVE-2025-27715 is a low-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 21 Mar 2025. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
Mattermost versions 9.11.x <= 9.11.8 fail to prompt for explicit approval before adding a team admin to a private channel, which team admins to joining private channels via crafted permalink links without explicit consent from them.
Weakness: CWE-863
Which versions are affected by CVE-2025-27715?
7 open source packages ship an affected version, including github.com/mattermost/mattermost/server/v8, mattermost and github.com/mattermost/mattermost-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/mattermost/mattermost/server/v8 Go | All versions | None |
github.com/mattermost/mattermost/server/v8 Go | From 9.11.0 | 9.11.9 |
github.com/mattermost/mattermost/server/v8 Go | From 9.11.0 | 9.11.9 |
mattermost Bitnami | From 9.11.0 | 10.0.0 |
github.com/mattermost/mattermost-server Go | From 9.11.0+incompatible | 9.11.9+incompatible |
github.com/mattermost/mattermost-server/v5 Go | All versions | None |
1 more packages
github.com/mattermost/mattermost-server/v6 Go | All versions | None |
Products include Mattermost Mattermost Server.
How do I fix CVE-2025-27715?
Upgrade github.com/mattermost/mattermost/server/v8 to 9.11.9 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2025-27715 being exploited?
There is no known exploitation of CVE-2025-27715 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 BIT-mattermost-2025-27715, GHSA-cw7q-5cgc-h3h9, GO-2025-3555.