WebSocket Origin Header Validation Bypass in Headroom

Executive Summary

This vulnerability is a Cross-Site WebSocket Hijacking (CSWSH) issue in the Headroom WebSocket server. It occurs because the server does not validate the Origin header of incoming WebSocket requests before forwarding them to the upstream OpenAI API. This allows malicious WebSocket clients to send arbitrary requests without authentication.

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Detection Guidance

Check Headroom server logs for unauthorized WebSocket connections without valid Origin headers. Inspect network traffic for WebSocket handshakes with missing or spoofed Origin fields. Use tools like Wireshark or tcpdump to monitor WebSocket connections to the Headroom proxy.

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Impact Analysis

An attacker could exploit this to perform unauthorized LLM requests, send arbitrary instructions or prompts, potentially leading to remote code execution, information disclosure, or quota exhaustion. This requires the attacker to execute a malicious WebSocket client in a browser with access to the Headroom proxy and an OpenAI API key stored in the environment.

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Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, information disclosure, or service disruption, which may violate compliance requirements under GDPR (data protection) and HIPAA (healthcare data privacy). Unauthorized LLM requests could expose personal or protected health information.

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Mitigation Strategies

Upgrade Headroom to version 0.35.0 or later immediately. Disable WebSocket proxy access if not required. Ensure OpenAI API keys are not stored in environment variables accessible to the Headroom proxy. Restrict network access to the Headroom server to trusted sources only.

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