CVE-2023-53016 is a vulnerability identified in the Linux kernel's Bluetooth subsystem, specifically within the RFCOMM protocol implementation. The issue arises from a potential deadlock condition in the function rfcomm_sk_state_change. The deadlock occurs due to improper lock acquisition order between two locks: the socket lock (sk lock) and the rfcomm lock. In the vulnerable code path, rfcomm_sock_connect acquires the sk lock first and then waits for the rfcomm lock, while rfcomm_sock_release holds the rfcomm lock and attempts to acquire the sk lock. This circular dependency can cause a deadlock, halting the progress of Bluetooth RFCOMM socket operations. The vulnerability was reported by syzbot, an automated kernel fuzzer. The fix involves dropping the sk lock before calling rfcomm_dlc_open to prevent the deadlock scenario, while maintaining the socket's reference count to avoid use-after-free issues after rfcomm_dlc_open completes. This patch ensures proper lock ordering and resource management, eliminating the deadlock risk in the Bluetooth RFCOMM socket state transitions. The vulnerability affects Linux kernel versions identified by the commit hash 1804fdf6e494e5e2938c65d8391690b59bcff897 and was published on March 27, 2025. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, this vulnerability primarily impacts systems running Linux kernels with Bluetooth RFCOMM support enabled. The deadlock can cause Bluetooth communication to freeze or become unresponsive, potentially disrupting services or applications relying on Bluetooth connectivity, such as IoT devices, industrial control systems, or user endpoint devices. While this vulnerability does not directly lead to privilege escalation or data leakage, the denial-of-service effect caused by deadlocks can degrade system availability and reliability. In environments where Bluetooth is critical for device communication or operational technology, this could lead to operational interruptions or degraded user experience. Additionally, embedded Linux devices with Bluetooth capabilities used in sectors like manufacturing, healthcare, or transportation across Europe could be affected. The lack of known exploits reduces immediate risk, but unpatched systems remain vulnerable to potential future exploitation or accidental deadlocks triggered by malformed Bluetooth traffic or device interactions.

European organizations should prioritize updating their Linux kernels to the patched versions that include the fix for CVE-2023-53016. Specifically, they should apply the kernel update containing the commit that drops the sk lock before rfcomm_dlc_open and maintains socket reference counts properly. For systems where immediate patching is not feasible, administrators can consider temporarily disabling Bluetooth RFCOMM support if it is not essential, thereby mitigating the risk of deadlocks. Monitoring system logs for Bluetooth-related errors or hangs can help detect potential deadlock occurrences. Additionally, organizations should implement robust testing of Bluetooth functionality after kernel updates to ensure stability. For embedded devices or appliances with Linux-based Bluetooth stacks, vendors should be engaged to provide firmware updates incorporating this fix. Network segmentation and limiting Bluetooth device pairing to trusted devices can reduce exposure. Finally, maintaining an inventory of Linux systems with Bluetooth enabled and tracking kernel versions will aid in prioritizing patch deployment.