CVE-2026-93851
High
Description
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10 fail to validate the target post ID in the Agents plugin's mention reminder component, which allows an authenticated user who can post in a channel visible to a system administrator to cause the administrator's browser to send an unintended API request, resulting in replacement of an installed plugin and code execution on the server, via a crafted post containing a forged mention reminder that the administrator clicks. Mattermost Advisory ID: MMSA-2026-00742
SeverityHigh
CVSS8.0
Exploit probability—
Product
Mattermost
PublishedOct 28, 2026
First seenNov 4, 2026
Weakness typeCWE-22Path traversal
How to fix
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Mattermost Mattermost | 11.9.0 ≤ v ≤ 11.9.1, 11.8.0 ≤ v ≤ 11.8.5, 11.7.0 ≤ v ≤ 11.7.10 | — |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.