Username Spoofing in Mattermost Plugin Bot Registration

Executive Summary

This vulnerability affects certain versions of Mattermost (11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, and 10.11.x <= 10.11.16) where the system fails to verify that a username returned during bot registration actually belongs to a bot account.

Because of this failure in validation, an unprivileged attacker can pre-register a user account with a predictable plugin bot username and intercept private messages sent by plugins via direct message channels.

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Impact Analysis

This vulnerability can allow an unprivileged attacker to intercept private messages that are intended to be sent between plugins and bot accounts.

As a result, sensitive or confidential information communicated via these direct message channels could be exposed to unauthorized parties.

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Mitigation Strategies

To mitigate this vulnerability, you should update Mattermost to a version later than 11.6.1, 11.5.4, or 10.11.16, as these versions contain the fix for the issue where username validation during bot registration was insufficient.

Additionally, monitor the Mattermost Security Updates page for any further patches or advisories.

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Compliance Impact

The vulnerability allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.

This interception of private messages could potentially lead to unauthorized access to sensitive information, which may impact compliance with data protection regulations such as GDPR and HIPAA that require the protection of personal and sensitive data.

However, the provided information does not explicitly state the direct effects on compliance with these standards.

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