Mattermost Host Header Injection Vulnerability in Slash Commands

A vulnerability exists in Mattermost versions 11.5.x through 11.5.1 and 10.11.x through 10.11.13, where the application fails to properly validate the Host header when generating response URLs for custom slash commands. This flaw allows an authenticated attacker to redirect the responses of slash commands to a server controlled by the attacker by spoofing the Host header.

Impact

Exploitation of this vulnerability could lead to unauthorized redirection of slash command responses to an attacker-controlled server.

Remediation

Users can upgrade to Mattermost versions 11.7.0 or 11.6.0 to address this vulnerability.