CVE-2025-5688 is a buffer overflow vulnerability classified under CWE-787, discovered in Amazon FreeRTOS version 2.3.4. It arises from improper handling of LLMNR (Link-Local Multicast Name Resolution) and mDNS (Multicast DNS) queries that contain excessively long DNS names. Specifically, when Buffer Allocation Scheme 1 is used and LLMNR or mDNS is enabled, the system fails to properly validate the length of incoming DNS names, leading to out-of-bounds writes in memory buffers. This can corrupt adjacent memory, potentially allowing attackers to execute arbitrary code, cause denial of service via system crashes, or escalate privileges. The vulnerability requires local network access (AV:L), no user interaction (UI:N), and no privileges (PR:N), but the attack complexity is low (AC:L) and partial attack prerequisites (AT:P) apply. The CVSS 4.0 base score is 7.5, reflecting high severity with high impact on confidentiality, integrity, and availability. No public exploits have been reported yet, but the vulnerability poses a significant risk to embedded and IoT devices running vulnerable FreeRTOS versions. The recommended remediation is to upgrade to the latest FreeRTOS release containing the fix and ensure any forks or derivative implementations incorporate the patch. Additionally, network segmentation and limiting exposure of LLMNR/mDNS services can reduce attack surface.

For European organizations, the impact of CVE-2025-5688 is considerable, especially for those deploying Amazon FreeRTOS in IoT devices, industrial control systems, and embedded environments. Exploitation could lead to unauthorized code execution, data leakage, or denial of service, undermining device reliability and network security. Critical infrastructure sectors such as manufacturing, energy, and transportation that rely on embedded systems are particularly vulnerable. Compromise of these devices could facilitate lateral movement within networks or disrupt operational technology environments. The vulnerability's local network attack vector means that attackers need access to the same network segment, which is common in enterprise and industrial settings. Given the widespread adoption of FreeRTOS in Europe’s growing IoT ecosystem, failure to patch could expose organizations to targeted attacks or supply chain risks.

1. Upgrade all affected Amazon FreeRTOS instances to the latest version that includes the patch for CVE-2025-5688. 2. Audit and patch any forks or derivative FreeRTOS codebases used internally or by third-party vendors to ensure the fix is applied. 3. Disable LLMNR and mDNS services on devices where these protocols are not required to reduce attack surface. 4. Implement network segmentation to isolate IoT and embedded devices from critical network segments, limiting local network exposure. 5. Employ strict network access controls and monitoring to detect anomalous LLMNR/mDNS traffic patterns indicative of exploitation attempts. 6. Conduct regular firmware and software integrity checks on embedded devices to detect unauthorized modifications. 7. Collaborate with device manufacturers and suppliers to ensure timely updates and vulnerability management in embedded products.