CVE-2026-12882

Name of the Vulnerable Software and Affected Versions Mattermost version 11.9.0 Mattermost version 11.8.4 Mattermost version 11.7.7 Mattermost version 10.11.22

Description An issue exists where the software fails to parse Markdown autolinks containing unmatched trailing closing parentheses in linear time. This allows an authenticated user with permissions to create posts to cause excessive server CPU consumption and degrade service availability for other users by submitting specially crafted post or message attachment content.

Recommendations Update Mattermost version 11.9.0 to a newer version. Update Mattermost version 11.8.4 to a newer version. Update Mattermost version 11.7.7 to a newer version. Update Mattermost version 10.11.22 to a newer version.