CVE-2023-53057 is a vulnerability identified in the Linux kernel's Bluetooth subsystem, specifically within the Host Controller Interface (HCI) synchronization code. The flaw arises from an out-of-bounds read in the function hci_init_stage_sync(), which iterates over a variable-length array of initialization stages for Bluetooth devices. The function assumes that each stage element is valid as long as the previous element's function pointer is valid. However, two arrays, amp_init1[] and amp_init2[], lack a terminating invalid element, unlike other similar arrays such as hci_init0[] and le_init2[]. This omission causes hci_init_stage_sync() to read beyond the valid bounds of amp_init1[] and amp_init2[], leading to a global out-of-bounds memory access. The bug was detected by Kernel Address Sanitizer (KASAN) during the execution of the hci_dev_open_sync() function, which is responsible for powering on and initializing Bluetooth HCI devices. The out-of-bounds read involves accessing memory beyond the allocated array, potentially causing undefined behavior, memory corruption, or kernel crashes. The patch fixes this by appending an empty invalid element to the end of amp_init1[] and amp_init2[], preventing the function from reading out of bounds. This vulnerability affects Linux kernel versions containing the faulty code, as identified by the commit hashes provided. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability is technical and low-level, related to kernel memory safety in Bluetooth device initialization.

For European organizations, the impact of CVE-2023-53057 depends largely on their use of Linux-based systems with Bluetooth capabilities. Many enterprises and public sector entities in Europe deploy Linux servers, desktops, and embedded devices that may include Bluetooth hardware. Exploitation of this vulnerability could lead to kernel crashes (denial of service) or potentially memory corruption, which might be leveraged for privilege escalation or arbitrary code execution by a local attacker. This risk is particularly relevant for organizations using Linux in environments where Bluetooth devices are enabled and accessible, such as in IoT deployments, industrial control systems, or office environments with Bluetooth peripherals. Disruption of critical services or compromise of sensitive systems could result if attackers exploit this flaw. However, the requirement for local code execution or interaction with Bluetooth initialization reduces the likelihood of remote exploitation. The vulnerability could also affect Linux distributions widely used in Europe, impacting sectors such as finance, healthcare, manufacturing, and government. The absence of known exploits currently limits immediate risk, but timely patching is essential to prevent future attacks.

European organizations should take the following specific mitigation steps: 1) Identify all Linux systems with Bluetooth enabled, including servers, desktops, laptops, and embedded devices. 2) Apply the official Linux kernel patches that add the terminating invalid elements to amp_init1[] and amp_init2[] arrays as soon as they are available from trusted Linux distribution vendors or kernel maintainers. 3) If immediate patching is not possible, consider disabling Bluetooth functionality on critical systems to reduce attack surface. 4) Monitor system logs for unusual Bluetooth initialization errors or kernel warnings related to hci_dev_open_sync. 5) Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar memory safety issues proactively. 6) Maintain up-to-date inventories of Linux kernel versions in use and subscribe to security advisories from Linux vendors and the CVE database. 7) Educate system administrators about the risks of Bluetooth-related kernel vulnerabilities and the importance of patch management. These targeted actions go beyond generic advice by focusing on Bluetooth subsystem awareness and kernel patch application.