CVE-2023-54210: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54210 is a use-after-free vulnerability in the Linux kernel's Bluetooth subsystem, specifically within the hci_sync component and the hci_remove_adv_monitor() function. The flaw was publicly disclosed on December 30, 2025, and affects Linux kernel versions prior to 6.1.42, 6.4.7, and 6.5. The vulnerability is triggered when msft_remove_monitor() frees the monitor structure while a subsequent debug log call (bt_dev_dbg()) under the HCI_ADV_MONITOR_EXT_MSFT case still references it. Feedly estimates the severity as HIGH, and the EPSS score is approximately 0.017% (very low exploitation probability) (Feedly, EUVD).

The root cause is a use-after-free memory error (CWE-416) in the Linux kernel Bluetooth HCI synchronization layer. The vulnerable call chain is: hci_remove_adv_monitor() → msft_remove_monitor() → msft_remove_monitor_sync() → msft_le_cancel_monitor_advertisement_cb() → hci_free_adv_monitor(), which frees the monitor structure. After this deallocation, the bt_dev_dbg() macro in the HCI_ADV_MONITOR_EXT_MSFT branch of hci_remove_adv_monitor() accesses the now-freed memory, as detected by KASAN (Kernel Address Sanitizer). The fix involves stashing the relevant data from the monitor structure before it is freed, eliminating the dangling pointer access (Feedly, EUVD).

Exploitation of this use-after-free could lead to kernel memory corruption, potentially causing a system crash (denial of service) or, in more severe scenarios, enabling privilege escalation or arbitrary code execution in kernel context. The vulnerability is confined to systems with Bluetooth hardware and the MSFT HCI extension enabled, limiting the affected asset scope. Given the kernel-level nature of the flaw, successful exploitation could grant an attacker full control over the affected system (Feedly, EUVD).

The Linux kernel project has released patches addressing this vulnerability in stable branches. Fixed versions include Linux kernel 6.1.42, 6.4.7, and 6.5. The patches are available via the upstream stable kernel repository at the following commits: 0d4d6b083da9b033ddccef72d77f373c819ae3ea, bf00c2c8f6254f44ac041aa9a311ae9e0caf692b, and de6dfcefd107667ce2dbedf4d9337f5ed557a4a1. Users and administrators should update to a patched kernel version; as a temporary workaround, disabling Bluetooth or the MSFT HCI extension (if not required) can reduce exposure (Kernel Stable, EUVD).