CVE-2024-39274: Mattermost

Medium severity, CVSS 6.5. 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, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels

Affected products

• Mattermost Mattermost: from 9.5.0, before 9.5.7 (fixed in 9.5.7); from 9.7.0, before 9.7.6 (fixed in 9.7.6); from 9.8.0, before 9.8.2 (fixed in 9.8.2); version 9.9.0 only

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