CVE-2026-10103

Name of the Vulnerable Software and Affected Versions Mattermost versions 11.7.0 through 11.7.2 Mattermost versions 11.6.0 through 11.6.4 Mattermost versions 10.11.0 through 10.11.19

Description The shared channel inbound sync handler fails to verify post ownership. This allows an authenticated remote cluster to modify or delete posts authored by local users or other remotes by sending crafted sync messages that reference arbitrary post IDs within channels shared with that remote.

Recommendations Update Mattermost versions 11.7.0 through 11.7.2 to a version newer than 11.7.2. Update Mattermost versions 11.6.0 through 11.6.4 to a version newer than 11.6.4. Update Mattermost versions 10.11.0 through 10.11.19 to a version newer than 10.11.19.