Is CVE-2026-93851 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-93851 being exploited in the wild.

How severe is CVE-2026-93851?

High severity, with a CVSS score of 8, published 28 October 2026.

Which products and versions are affected?

Mattermost Server 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10.

Is there a fix for CVE-2026-93851?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-93851 attacked?

It is attacked over the network, in a web application.

Am I affected by CVE-2026-93851?

Check whether you run Mattermost Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-93851: Mattermost CSRF via Agents plugin mention reminder validation

Q: Is there a fix for CVE-2026-93851?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

Q: How is CVE-2026-93851 attacked?

It is attacked over the network, in a web application.

Q: Am I affected by CVE-2026-93851?

Check whether you run Mattermost Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-93851 · Severity: high · CVSS 8 · Published 2026-10-28

Mattermost is a self-hosted team collaboration platform used by organizations for internal communications. A flaw in the Agents plugin's mention reminder allows an authenticated user to craft a malicious post that tricks an administrator into performing unintended actions, such as installing a malicious plugin, when the administrator interacts with the post. An attacker can exploit this to achieve remote code execution on the Mattermost server.

Technologies: Mattermost Server. Vendors: Mattermost.

Quick answers

Is CVE-2026-93851 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-93851 being exploited in the wild.
How severe is CVE-2026-93851?: High severity, with a CVSS score of 8, published 28 October 2026.
Which products and versions are affected?: Mattermost Server 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10.
Is there a fix for CVE-2026-93851?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-93851 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2026-93851?: Check whether you run Mattermost Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is a cross-site request forgery (CSRF) in the Agents plugin's mention reminder component, caused by insufficient validation of the target post ID. An authenticated attacker who can post in a channel visible to a system administrator crafts a forged mention reminder that, when clicked by the administrator, causes the browser to send unintended API requests with the administrator's credentials. This allows replacement of an installed plugin and arbitrary code execution on the server.

Affected products

Mattermost Mattermost Server 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10

Timeline

2026-10-28: disclosed: Security advisory published

References

https://mattermost.com/security-updates

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.