CVE-2025-21937 is a vulnerability identified in the Linux kernel's Bluetooth management subsystem. Specifically, the issue arises in the function mgmt_remote_name(), which is responsible for handling remote Bluetooth device name requests. The vulnerability is due to the lack of a proper check on the return value of mgmt_alloc_skb(), a function that allocates socket buffers (sk_buff) used for Bluetooth management messages. Without verifying the success of this allocation, the kernel code could dereference a null pointer if mgmt_alloc_skb() fails, leading to a null pointer dereference (NPD). This type of flaw can cause the affected kernel to crash or become unstable, resulting in a denial of service (DoS) condition. The patch involves adding a check to ensure mgmt_alloc_skb() returns a valid pointer before it is used in mgmt_remote_name(), thereby preventing the null pointer dereference. The vulnerability affects multiple versions of the Linux kernel, as indicated by the commit hashes listed, and was publicly disclosed on April 1, 2025. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet. The vulnerability does not require user interaction or authentication to be triggered, as it can be exploited by sending crafted Bluetooth management messages to the vulnerable system's Bluetooth interface.

For European organizations, the impact of CVE-2025-21937 primarily revolves around availability. Systems running vulnerable Linux kernel versions with Bluetooth enabled could be forced into a kernel panic or crash by an attacker within Bluetooth range, causing temporary denial of service. This could disrupt critical services, especially in environments where Linux servers or embedded devices rely on Bluetooth for management or communication, such as industrial control systems, healthcare devices, or IoT deployments. While the vulnerability does not directly compromise confidentiality or integrity, the resulting service disruption could have downstream effects on business operations, safety systems, or user productivity. The risk is heightened in sectors with high Bluetooth usage or where physical proximity to devices is feasible for attackers, including manufacturing plants, offices, and public spaces. Since no known exploits exist yet, the immediate threat level is moderate, but the potential for future exploitation warrants prompt attention.

To mitigate CVE-2025-21937, European organizations should: 1) Apply the official Linux kernel patches that add the necessary null pointer checks in mgmt_remote_name() as soon as they become available from trusted sources or distributions. 2) If patching is not immediately possible, consider disabling Bluetooth functionality on critical Linux systems, especially those exposed in environments where attackers could gain physical proximity. 3) Implement network segmentation and physical security controls to limit unauthorized access to Bluetooth interfaces. 4) Monitor system logs and kernel messages for signs of Bluetooth-related crashes or anomalies. 5) For embedded or IoT devices running vulnerable kernels, coordinate with vendors for firmware updates or mitigations. 6) Educate IT and security teams about the vulnerability to ensure rapid response and awareness. These steps go beyond generic advice by emphasizing physical security, monitoring, and vendor coordination tailored to the Bluetooth-specific nature of the vulnerability.