CVE-2026-28741 CSRF Protection Bypass Allows Updating a User's Authentication Method

What is CVE-2026-28741?

CVE-2026-28741 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 15 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Mattermost versions 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to validate CSRF tokens on an authentication endpoint which allows an attacker to update a user's authentication method via a CSRF attack by tricking a user into visiting a malicious page. Mattermost Advisory ID: MMSA-2026-00625

Weakness: CWE-352

Which versions are affected by CVE-2026-28741?

12 open source packages ship an affected version, including github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server and github.com/mattermost/mattermost-server/v5. It affects 1 product.

Products include Mattermost Mattermost Server.

How do I fix CVE-2026-28741?

Upgrade github.com/mattermost/mattermost/server/v8 to a fixed version for your release line: 11.3.3, 11.4.3, 11.5.0 or 8.0.0-20260220133927-c29cf05d40f8.

Is CVE-2026-28741 being exploited?

There is no known exploitation of CVE-2026-28741 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-m7cf-4gh2-v4qg, GO-2026-5495.