CVE-2026-4053: Mattermost Server

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce the PostEditTimeLimit on non-message post fields which allows an authenticated user to modify post file attachments, props, and pin status after the edit window has expired via the post patch and update API endpoints.. Mattermost Advisory ID: MMSA-2026-00631

Affected products

• Mattermost Mattermost Server: from 10.11.0, before 10.11.14 (fixed in 10.11.14); from 11.5.0, before 11.5.2 (fixed in 11.5.2)

Published 2026-05-15. Last modified 2026-06-17.