CVE-2025-12559 Information Disclosure in Common Teams API

What is CVE-2025-12559?

CVE-2025-12559 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 27 Nov 2025. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint

Weakness: CWE-200

Which versions are affected by CVE-2025-12559?

14 open source packages ship an affected version, including github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5 and github.com/mattermost/mattermost-server/v6. It affects 1 product.

Products include Mattermost Mattermost Server.

How do I fix CVE-2025-12559?

Upgrade github.com/mattermost/mattermost-server to a fixed version for your release line: 10.11.5, 10.12.2, 10.5.13 or 11.0.3.

Is CVE-2025-12559 being exploited?

There is no known exploitation of CVE-2025-12559 in the wild and no public exploit code.

Other vulnerabilities in Mattermost Mattermost Server

• CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers Critical 9.9
• CVE-2025-12421 Account Takeover via Code Exchange Endpoint Critical 9.9
• CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User Critical 9.9
• CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards Critical 9.9
• CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive Critical 9.9

All Mattermost Mattermost Server vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-4g87-9x45-cx2h, GO-2025-4169.