Executive Summary

This vulnerability exists in Mattermost versions 11.5.x up to 11.5.1, 10.11.x up to 10.11.13, and 11.4.x up to 11.4.3. It occurs because the software fails to enforce uniqueness of slash command trigger words during command updates.

An authenticated team member who has the 'Manage Own Slash Commands' permission can exploit this by editing their own slash command trigger to a trigger word that is already registered by the system or another custom command. This allows them to hijack and impersonate existing slash commands.

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Impact Analysis

The vulnerability allows an authenticated user with specific permissions to hijack and impersonate existing system or custom slash commands. This can lead to confusion or misuse within the team environment, as commands may execute unintended actions or mislead users.

While the CVSS score indicates no impact on confidentiality or availability, it does have a low impact on integrity, meaning the commands' behavior can be altered maliciously.

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Mitigation Strategies

To mitigate this vulnerability, you should update Mattermost to a version later than the affected versions (11.5.1, 10.11.13, 11.4.3) where the issue is fixed.

Additionally, review and restrict permissions related to 'Manage Own Slash Commands' to trusted users only, as the vulnerability allows authenticated team members with this permission to hijack slash commands.

Stay informed about security updates by monitoring Mattermost's official security updates page.

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