CVE-2025-37816 is a vulnerability identified in the Linux kernel's Management Engine Interface (MEI) Virtual Serial Channel (VSC) driver, specifically in the handling of buffer sizes within the vsc_tp_packet structure. The issue arises from incorrect use of the __counted_by(len) attribute introduced in GCC 15, which is intended to help the compiler enforce buffer size correctness. The vulnerability occurs because the 'len' parameter represents the actual packet length excluding the cyclic redundancy check (CRC), but the code incorrectly assumes it includes the CRC. When the vsc_tp_xfer() function attempts to append the CRC to the buffer, it triggers a buffer overflow detected by the fortify-source mechanism, resulting in a fortify-panic. This panic is a security feature that prevents buffer overflows by terminating the process when an overflow is detected. The root cause is a mismatch between the buffer size annotation and the actual buffer usage, leading to an out-of-bounds write attempt. The fix involves restructuring the vsc_tp_packet definition by splitting it into a header and a full-packet definition with a fixed-size buffer, allowing fortify-source to continue providing buffer overrun protection without false positives or unsafe behavior. This vulnerability does not appear to have known exploits in the wild yet, but it affects the Linux kernel, which is widely used across many systems. The vulnerability could potentially lead to denial of service (via kernel panic) or other undefined behavior if exploited, impacting system stability and security.

For European organizations, the impact of CVE-2025-37816 can be significant due to the widespread use of Linux in servers, cloud infrastructure, embedded systems, and critical industrial environments. A buffer overflow in the kernel MEI VSC driver could cause system crashes or kernel panics, leading to denial of service conditions. This is particularly critical for sectors relying on high availability and real-time processing such as telecommunications, finance, healthcare, and manufacturing. Additionally, while no known exploits exist currently, the vulnerability could be leveraged by attackers with local access or through compromised components to escalate privileges or disrupt operations. The MEI interface is often used for communication with Intel Management Engine hardware, which is present in many enterprise-grade systems, increasing the potential attack surface. European organizations operating critical infrastructure or cloud services could face operational disruptions, reputational damage, and compliance challenges if this vulnerability is exploited.

Mitigation should focus on applying the official Linux kernel patches that address this vulnerability by correcting the buffer size handling in the MEI VSC driver. Organizations should: 1) Identify all Linux systems running affected kernel versions and prioritize patching those with MEI VSC enabled or in use. 2) Test patches in staging environments to ensure stability before deployment. 3) Monitor kernel logs for fortify-panic or buffer overflow messages that might indicate attempts to trigger this vulnerability. 4) Restrict local access to systems to trusted users only, as exploitation likely requires local code execution or privileged access. 5) Employ kernel hardening techniques such as enabling kernel lockdown mode and using security modules (e.g., SELinux, AppArmor) to limit the impact of potential exploits. 6) Maintain up-to-date intrusion detection and prevention systems to detect anomalous behavior related to kernel crashes or MEI interface misuse. 7) Engage with hardware and Linux distribution vendors to ensure timely updates and guidance.