CVE-2024-29977: Mattermost

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

Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6 fail to properly validate synced reactions, when shared channels are enabled, which allows a malicious remote to create arbitrary reactions on arbitrary posts

Affected products

• Mattermost Mattermost: from 9.5.0, before 9.5.7 (fixed in 9.5.7); version 9.9.0 only

Published 2024-08-01. Last modified 2026-06-17.