CVE-2022-50386: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-50386 is a use-after-free vulnerability in the Linux kernel's Bluetooth L2CAP (Logical Link Control and Adaptation Protocol) subsystem. The flaw occurs when handling Bluetooth channel operations — specifically, a channel reference obtained via __l2cap_get_chan_blah() can be freed before it is fully used, leading to memory corruption detectable via KASAN. It was publicly disclosed on September 18, 2025, and affects Linux kernel versions from 4.9 up through 6.0.x across multiple stable branches. The vulnerability carries a CVSS v3.1 base score of 8.0 (High) (RedHat CVE, Feedly).

The root cause is a classic use-after-free condition (CWE-416) in l2cap_core.c. After calling __l2cap_get_chan_blah() to retrieve an L2CAP channel pointer, the channel's reference count is not atomically incremented before use, allowing a concurrent l2cap_chan_destroy() to free the underlying memory. A subsequent mutex lock operation then reads from the freed memory region, as captured in the KASAN trace: BUG: KASAN: use-after-free in __mutex_lock+0x278/0x400. The fix applies l2cap_chan_hold_unless_zero() immediately after channel retrieval to safely increment the reference count only if the object is still alive. Exploitation requires adjacent network access (Bluetooth range) and low-level privileges (RedHat CVE, Kernel Patch).

Successful exploitation could allow an attacker within Bluetooth range with low privileges to cause memory corruption, potentially leading to arbitrary code execution, system crashes (denial of service), or unauthorized access to sensitive kernel memory. All three security dimensions — confidentiality, integrity, and availability — are rated High in the CVSS assessment. The vulnerability affects any Bluetooth-enabled Linux system running a vulnerable kernel version, which encompasses a broad range of servers, desktops, embedded devices, and IoT systems (RedHat CVE, Feedly).

Patches are available across all affected stable kernel branches. Administrators should update to the following minimum versions: 4.9.331, 4.14.296, 4.19.262, 5.4.220, 5.10.150, 5.15.75, 5.19.17, 6.0.3, or 6.1+ (Kernel Patch, RedHat CVE). Vendor-specific updates are available from Red Hat (RHSA-2025:19102, RHSA-2025:21083, RHSA-2025:22006, and others), SUSE, AlmaLinux, Oracle Linux, and Rocky Linux. As a temporary workaround where patching is not immediately possible, disabling Bluetooth entirely (rfkill block bluetooth) or restricting Bluetooth pairing to trusted devices reduces exposure. Applying kernel security updates promptly and monitoring for suspicious Bluetooth-related kernel activity is also recommended.