CVE-2024-31030: FreeCoAP DoS Vulnerability

CVE-2024-31030 Overview

A null pointer dereference vulnerability exists in coap_msg.c within Keith Cullen's FreeCoAP v.0.7. This flaw allows remote attackers to cause a Denial of Service (DoS) or potentially disclose sensitive information by sending specially crafted CoAP packets to the affected system.

Critical Impact

Remote attackers can exploit this vulnerability without authentication to crash FreeCoAP services or leak memory contents, potentially exposing sensitive data from IoT devices and embedded systems.

Affected Products

• Keith-cullen FreeCoAP v.0.7
• Systems implementing FreeCoAP for CoAP (Constrained Application Protocol) communications
• IoT devices and embedded systems utilizing the vulnerable library

Discovery Timeline

• 2024-05-31 - CVE CVE-2024-31030 published to NVD
• 2025-06-20 - Last updated in NVD database

Technical Details for CVE-2024-31030

Vulnerability Analysis

This vulnerability is classified as CWE-476 (NULL Pointer Dereference), a memory corruption issue that occurs when the application attempts to dereference a pointer that has a null value. In FreeCoAP v.0.7, the vulnerable code resides in the coap_msg.c file, which handles CoAP message parsing and processing.

The vulnerability is network-exploitable without requiring any authentication or user interaction, making it particularly dangerous for Internet-facing CoAP deployments. When a malformed CoAP packet is received, the message processing logic fails to properly validate pointer values before dereferencing, leading to either a crash (DoS) or potential memory disclosure depending on the exploitation technique used.

CoAP (Constrained Application Protocol) is widely deployed in IoT environments for lightweight machine-to-machine communication, making this vulnerability significant for smart home devices, industrial sensors, and other constrained network devices.

Root Cause

The root cause of this vulnerability is improper input validation in the CoAP message parsing routine within coap_msg.c. The code fails to adequately check for null pointer conditions before accessing memory, which can be triggered by sending malformed or edge-case CoAP packets. This represents a classic memory safety issue common in C-based network protocol implementations.

Attack Vector

The attack vector is network-based, requiring the attacker to send specially crafted CoAP packets to a vulnerable FreeCoAP instance. The attack can be executed remotely without authentication, and no user interaction is required. An attacker needs only network access to the CoAP service, typically running on UDP port 5683 or 5684 (for DTLS).

The exploitation mechanism involves crafting a CoAP message that causes the parser to reach a code path where a null pointer is dereferenced. This can be achieved by manipulating CoAP message options, payload boundaries, or header fields in unexpected ways. For detailed technical information, refer to the GitHub Issue Discussion.

Detection Methods for CVE-2024-31030

Indicators of Compromise

• Unexpected crashes or restarts of FreeCoAP-based services
• Core dumps or crash reports originating from coap_msg.c or CoAP message handling routines
• Unusual CoAP traffic patterns with malformed packets targeting ports 5683 or 5684
• Segmentation fault logs associated with the FreeCoAP process

Detection Strategies

• Deploy network intrusion detection systems (IDS) with signatures for malformed CoAP packets
• Implement deep packet inspection on CoAP traffic to identify protocol anomalies
• Monitor system logs for segmentation faults and null pointer dereference crashes in FreeCoAP processes
• Use memory sanitizers (ASan, MSan) in development environments to detect exploitation attempts

Monitoring Recommendations

• Enable verbose logging for CoAP services to capture malformed packet details
• Configure process monitoring to alert on unexpected FreeCoAP service restarts
• Implement network flow analysis to detect scanning or fuzzing activity on CoAP ports
• Set up core dump analysis automation to identify exploitation patterns

How to Mitigate CVE-2024-31030

Immediate Actions Required

• Assess all deployments using FreeCoAP v.0.7 and prioritize remediation based on exposure
• Restrict network access to CoAP services using firewall rules to limit attack surface
• Implement network segmentation to isolate IoT devices running vulnerable FreeCoAP versions
• Consider deploying a CoAP proxy or gateway that can filter malformed packets

Patch Information

As of the last update, users should review the GitHub Issue Discussion for patch status and remediation guidance from the maintainer. Organizations should monitor the FreeCoAP repository for updates addressing this null pointer dereference vulnerability in coap_msg.c.

Workarounds

• Deploy network-level filtering to drop malformed CoAP packets before they reach vulnerable services
• Use a reverse proxy or CoAP gateway that performs strict protocol validation
• Implement rate limiting on CoAP endpoints to reduce the impact of DoS exploitation attempts
• Consider migrating to alternative CoAP implementations if patches are not available

# Example firewall rule to restrict CoAP access
# Limit CoAP traffic to trusted networks only
iptables -A INPUT -p udp --dport 5683 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p udp --dport 5683 -j DROP
iptables -A INPUT -p udp --dport 5684 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p udp --dport 5684 -j DROP