CVE-2025-5688 is a high-severity vulnerability identified in Amazon FreeRTOS version 2.3.4, categorized under CWE-787 (Out-of-bounds Write). The flaw arises from a buffer overflow condition triggered when processing Link-Local Multicast Name Resolution (LLMNR) or Multicast DNS (mDNS) queries containing excessively long DNS names. Specifically, this vulnerability affects systems that utilize Buffer Allocation Scheme 1 with LLMNR or mDNS enabled. The out-of-bounds write can corrupt adjacent memory, potentially leading to unpredictable behavior such as system crashes, denial of service, or arbitrary code execution. The vulnerability does not require authentication or user interaction, and the attack vector is local (AV:L), meaning the attacker must have local access to the device or network segment to send crafted LLMNR or mDNS queries. The CVSS 4.0 score of 7.5 reflects the high impact on confidentiality, integrity, and availability, with low attack complexity but requiring physical or logical local access. No known exploits in the wild have been reported yet, but the nature of the flaw suggests that exploitation could allow attackers to compromise embedded IoT devices running vulnerable FreeRTOS versions. The vulnerability is particularly relevant for embedded systems and IoT devices using Amazon FreeRTOS with network name resolution features enabled, which are common in industrial, consumer, and smart home environments.

For European organizations, the impact of CVE-2025-5688 can be significant, especially those deploying IoT devices or embedded systems based on Amazon FreeRTOS in critical infrastructure, manufacturing, healthcare, or smart city applications. Exploitation could lead to device malfunction, data corruption, or unauthorized control over devices, undermining operational continuity and safety. Given the local attack vector, attackers with network access (e.g., insider threats or compromised local devices) could leverage this vulnerability to escalate privileges or disrupt services. This could affect supply chain integrity and operational technology environments, which are increasingly targeted in Europe. The confidentiality, integrity, and availability of sensitive data and control systems could be compromised, leading to potential regulatory and compliance issues under GDPR and NIS Directive frameworks. The absence of known exploits reduces immediate risk but does not preclude targeted attacks, especially as IoT adoption grows across European industries.

Organizations should promptly upgrade all Amazon FreeRTOS deployments to the latest patched version that addresses CVE-2025-5688. For derivative or forked versions of FreeRTOS, ensure that the patch is backported and integrated. Disable LLMNR and mDNS services if they are not essential to reduce the attack surface. Implement network segmentation and strict access controls to limit local network exposure of vulnerable devices. Employ intrusion detection systems capable of monitoring unusual LLMNR or mDNS traffic patterns. Conduct regular firmware audits and vulnerability assessments on embedded devices. For critical environments, consider deploying endpoint protection solutions tailored for IoT devices to detect anomalous behavior. Finally, establish incident response procedures specific to IoT device compromise scenarios.