CVE-2026-3108 Terminal Escape Injection in mmctl Report Posts Command

What is CVE-2026-3108?

CVE-2026-3108 is a high-severity vulnerability in Mattermost Mattermost Server, published on 26 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences that enable screen manipulation, fake prompts, and clipboard hijacking.. Mattermost Advisory ID: MMSA-2026-00599

Weakness: CWE-150

Which versions are affected by CVE-2026-3108?

14 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-2026-3108?

Upgrade github.com/mattermost/mattermost/server/v8 to a fixed version for your release line: 10.11.11, 11.2.3, 11.3.2 or 11.4.1.

Is CVE-2026-3108 being exploited?

There is no known exploitation of CVE-2026-3108 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-3439-vqgj-2gcf, GO-2026-5067.