Mattermost Vulnerabilities: Remote Attack Possible

CERT-Bund has released Security Advisory WID-SEC-2026-0745 detailing multiple vulnerabilities in various versions of Mattermost Server. The advisory indicates a CVSS base score of 7.3 (high) and a temporal score of 6.4 (medium), with the possibility of remote attacks. Affected versions include Mattermost Server prior to 11.4.0, 11.3.1, 11.2.3, 10.11.11, 11.6.0, 10.11.13, 11.5.1, 11.4.3, and 10.11.13, impacting Linux, UNIX, and Windows operating systems.

Organizations using affected Mattermost Server versions should prioritize updating to a patched version to mitigate the risk of security bypass and unspecified impacts. While specific mitigation steps beyond updating are not detailed, prompt patching is the recommended course of action to prevent exploitation by attackers. Failure to update may expose sensitive communication data and system integrity to compromise.