Null Pointer Dereference in ccoap Due to Race Condition

Executive Summary

This is a null pointer dereference vulnerability caused by a race condition in the server-side session management of ccoap. When the request dispatch thread and session cleanup thread access shared session list nodes without synchronization, one thread may dereference a session pointer while the other clears its data, causing a segmentation fault.

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Detection Guidance

Detecting this vulnerability requires monitoring for crashes in the ccoap server process, particularly under concurrent request loads. Check server logs for segmentation faults or null pointer dereference errors. Use tools like gdb to attach to the running process and inspect stack traces during crashes. Enable core dumps for post-mortem analysis if the server crashes.

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Impact Analysis

A remote attacker could exploit this flaw to crash the CoAP server by triggering the race condition, resulting in a denial-of-service (DoS) attack. This would make the server unavailable for legitimate users.

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Mitigation Strategies

Apply a patch to the ccoap component that adds proper synchronization mechanisms (e.g., mutex locks) when accessing shared session list nodes. Alternatively, disable session management features if not required. Monitor server stability closely after changes and consider upgrading to a patched version of microcoap if available.

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