CVE-2026-2461 Missing authorization check allows unauthorized modification of other users' comments on a board

What is CVE-2026-2461?

CVE-2026-2461 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 16 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

Mattermost Plugins versions <=11.3 11.0.3 11.2.2 10.10.11.0 fail to implement authorisation checks on comment block modifications, which allows an authorised attacker with editor permission to modify comments created by other board members. Mattermost Advisory ID: MMSA-2025-00559

Weakness: CWE-639

Which versions are affected by CVE-2026-2461?

3 open source packages ship an affected version, including github.com/mattermost/mattermost-plugin-boards. It affects 1 product.

Products include Mattermost Mattermost Server.

How do I fix CVE-2026-2461?

Upgrade github.com/mattermost/mattermost-plugin-boards to 0.0.0-20260108044135-57c5be5b6ef5 or later.

Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.

Is CVE-2026-2461 being exploited?

There is no known exploitation of CVE-2026-2461 in the wild and no public exploit code.

Public exploit code: 1 proofs of concept on GitHub.

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-hf8w-x9h5-5gf9, GO-2026-4782.