CVE-2023-51847

What it actually does

A flaw in the coap_context_t function within src/coap_threadsafe.c allows remote unauthenticated attackers to trigger a denial of service by sending crafted CoAP requests that crash or hang the library's thread-safe context handling.

Why it matters to the business

Services and devices relying on Libcoap for constrained network communications can experience sudden unavailability, resulting in operational downtime for IoT, monitoring, or control systems with potential revenue or safety implications.

How an attack unfolds

An attacker identifies a reachable CoAP endpoint using Libcoap, crafts and transmits specially formed requests that exercise the vulnerable thread-safe context code path, and causes the target process to terminate or become unresponsive.

How to fix it

Upgrade Libcoap to a patched release that resolves the thread-safety defect in coap_context_t; apply vendor or community fixes as they become available and rebuild dependent applications.

How to confirm the fix worked

Confirm the installed Libcoap commit is newer than a3ed466, recompile applications, and perform functional testing with malformed CoAP traffic to verify the denial-of-service condition no longer occurs.

Typical attack path

1. Locate publicly reachable CoAP services
2. Send crafted CoAP packets targeting the coap_context_t implementation
3. Trigger resource exhaustion or crash in the thread-safe layer
4. Confirm loss of service availability

How to detect it

Examine application and system logs for abrupt crashes or restarts of processes linked to Libcoap, correlate with spikes in inbound CoAP traffic, and review network flow data for repeated requests from the same sources.

What your security team should do

• Prioritize patching Libcoap in all environments handling CoAP traffic
• Restrict network exposure of CoAP endpoints through firewalls or proxies
• Enable application crash reporting and monitor for sudden restarts