CVE-2024-40493 is a vulnerability identified in Keith Cullen FreeCoAP version 1.0, specifically within the coap_client_exchange_blockwise2 function. The flaw arises when the function coap_msg_get_payload(resp) returns a null pointer due to a specially crafted CoAP packet sent by a remote attacker. This null pointer is subsequently dereferenced in a memcpy operation, causing a null pointer dereference (CWE-476). This can lead to a denial of service (DoS) by crashing the application or, under certain conditions, potentially enable arbitrary code execution if the attacker can control the memory copied or exploit the crash to execute malicious payloads. The vulnerability is exploitable remotely over the network without requiring any authentication or user interaction, making it accessible to unauthenticated attackers. The CVSS 3.1 base score is 5.3, indicating a medium severity primarily due to the lack of confidentiality or integrity impact but with a clear availability impact. No patches or fixes have been published at the time of disclosure, and no known exploits are currently active in the wild. The vulnerability affects FreeCoAP 1.0, a lightweight CoAP implementation commonly used in IoT and constrained network environments, which are often deployed in industrial, smart city, and other embedded systems.

The primary impact of CVE-2024-40493 is denial of service, which can disrupt critical IoT and embedded systems relying on FreeCoAP 1.0 for communication. This disruption can affect availability of services in smart devices, industrial control systems, and other constrained environments. In some scenarios, the vulnerability may be leveraged for arbitrary code execution, potentially allowing attackers to take control of affected devices, leading to further compromise, data manipulation, or pivoting within networks. Given the widespread adoption of CoAP in IoT ecosystems, this vulnerability could affect a broad range of devices globally, impacting operational continuity and safety in sectors such as manufacturing, energy, transportation, and smart infrastructure. The lack of authentication requirements and remote exploitability increase the risk of automated or widespread attacks. However, the absence of known exploits and patches currently limits immediate impact but underscores the need for proactive mitigation.

Organizations should immediately audit their environments to identify any deployments of Keith Cullen FreeCoAP 1.0, especially in IoT and embedded systems. Until an official patch is released, network-level mitigations should be applied, such as filtering or blocking suspicious CoAP traffic from untrusted sources using firewalls or intrusion prevention systems. Implement strict network segmentation to isolate vulnerable devices and reduce exposure to external networks. Monitoring network traffic for anomalous CoAP packets that could trigger the vulnerability is recommended. Developers and integrators should consider upgrading to alternative CoAP implementations with active maintenance or applying custom patches to handle null pointer checks before memcpy operations. Additionally, applying runtime protections such as memory safety tools or sandboxing vulnerable components can reduce exploitation risk. Organizations should stay alert for vendor patches or updates and apply them promptly once available.