stoatchat Missing Authorization in Subscribe Message Handler

Executive Summary

This vulnerability is a missing authorization flaw in the Subscribe message handler of stoatchat versions before 0.15.0. It allows authenticated attackers to bypass access controls and subscribe to private servers they are not members of. By sending a Subscribe message with an arbitrary server ID, attackers can receive live UserUpdate events containing sensitive member information such as display names, avatars, and status changes.

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Detection Guidance

To detect this vulnerability, monitor network traffic for unauthorized Subscribe messages targeting private server topics. Check Redis topics for unexpected subscriptions to member-update channels. Inspect logs for repeated failed subscription attempts or unusual session activity.

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Impact Analysis

This vulnerability allows attackers to monitor private servers and enumerate members without membership, exposing sensitive user data like display names, avatars, and status updates. Even banned or kicked users' profiles can be monitored. Attackers only need a valid session token to exploit this issue.

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Compliance Impact

This vulnerability likely violates compliance requirements for data protection regulations such as GDPR and HIPAA due to unauthorized access to sensitive user data. It enables unauthorized surveillance and disclosure of personal information, which could result in legal penalties and reputational damage.

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Mitigation Strategies

Upgrade stoatchat to version 0.15.0 or later immediately. Review and restrict access to Redis topics and Bonfire's Autumn CDN. Implement strict membership verification in the Subscribe handler before allowing subscriptions to private servers.

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