DoS via Unauthenticated ZeroMQ Message in SGLang

Executive Summary

This is a denial-of-service (DoS) vulnerability in SGLang caused by missing input validation for AUX_DATA ZeroMQ control messages in the Decode worker. An unauthenticated remote attacker with network access to the Decode control PULL socket can send a malformed message to terminate the Decode control thread and disrupt the target server.

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Detection Guidance

Monitor for unexpected termination of the Decode control thread or failed inference requests. Check logs for uncaught IndexError messages related to kv_args.aux_data_ptrs or ZeroMQ control socket activity. Inspect network traffic on the Decode worker's ZeroMQ control port for malformed AUX_DATA multipart messages.

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Impact Analysis

Exploitation can cause inference requests to fail and time out, disrupting service for users relying on SGLang deployments with Prefill/Decode disaggregation. The Decode process and HTTP health endpoints remain operational, but end-to-end inference requests are affected.

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Mitigation Strategies

Restrict network access to the Decode worker's ZeroMQ control port. Implement input validation for AUX_DATA messages and bounds checking for buffer_index. Update SGLang to a patched version if available. Monitor health endpoints for failures and isolate affected components.

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