CVE-2022-49136 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_sync: Fix queuing commands when HCI_UNREGISTER is set
hci_cmd_sync_queue shall return an error if HCI_UNREGISTER flag has been set as that means hci_unregister_dev has been called so it will likely cause a uaf after the timeout as the hdev will be freed.
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Analysis
by VulDB Data Team • 08/27/2025
The vulnerability identified as CVE-2022-49136 resides within the Linux kernel's Bluetooth subsystem, specifically affecting the hci_sync module responsible for handling Bluetooth command synchronization. This flaw represents a critical race condition and use-after-free scenario that can be exploited to compromise system integrity and potentially execute arbitrary code. The issue manifests when the HCI_UNREGISTER flag is set, indicating that the Bluetooth device has been unregistered but commands may still be queued for execution. The vulnerability stems from the hci_cmd_sync_queue function failing to properly check for the HCI_UNREGISTER flag before queuing commands, creating a dangerous state where operations might proceed against a device that has already been freed from memory. This condition violates fundamental memory safety principles and can lead to unpredictable behavior including system crashes or privilege escalation.
The technical flaw occurs at the intersection of device lifecycle management and command queuing mechanisms within the Bluetooth subsystem. When hci_unregister_dev is invoked to remove a Bluetooth device from the system, it sets the HCI_UNREGISTER flag to signal that the device structure is being torn down. However, the hci_cmd_sync_queue function does not properly validate this flag before adding new commands to the queue, creating a temporal gap where commands can be scheduled for execution against a device that may be partially or fully deallocated. This race condition allows for a use-after-free condition where subsequent operations attempt to access memory that has already been freed, potentially leading to memory corruption and system instability. The vulnerability is classified under CWE-416 as Use After Free, which represents one of the most dangerous classes of memory safety issues in kernel space code. The flaw demonstrates poor state management and inadequate synchronization mechanisms between device registration and command processing components.
The operational impact of CVE-2022-49136 extends beyond simple system instability to potential privilege escalation and denial of service attacks. An attacker who can trigger the conditions leading to this vulnerability may be able to execute arbitrary code with kernel privileges, effectively compromising the entire system. The vulnerability is particularly concerning because it can be triggered through normal Bluetooth operations, making it exploitable in both physical and network-based attack scenarios. In environments where Bluetooth is enabled by default or frequently used, this vulnerability represents a significant risk to system security and availability. The use-after-free condition can result in memory corruption that may be leveraged to bypass security mechanisms such as kernel address space layout randomization and control flow integrity protections. From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.006 for Command and Scripting Interpreter: PowerShell and similar techniques that exploit kernel vulnerabilities to gain elevated privileges. The impact is further amplified by the fact that the Linux kernel is widely deployed across various platforms including servers, desktops, and embedded systems.
Mitigation strategies for CVE-2022-49136 focus on both immediate patching and operational hardening measures. The primary solution involves applying the kernel patch that ensures hci_cmd_sync_queue returns an error when the HCI_UNREGISTER flag is detected, preventing commands from being queued against unregistered devices. System administrators should prioritize updating their Linux kernels to versions containing the fix, particularly in environments where Bluetooth functionality is enabled and potentially exposed to untrusted users or networks. Additional mitigations include implementing proper Bluetooth device lifecycle management procedures, monitoring for unusual Bluetooth activity patterns, and employing kernel hardening techniques such as disabling unnecessary Bluetooth functionality when not required. Organizations should also consider implementing network segmentation to limit Bluetooth access to trusted environments and deploying intrusion detection systems that can monitor for suspicious kernel-level activity. The vulnerability serves as a reminder of the importance of proper synchronization and state validation in kernel space code, particularly in subsystems that handle device lifecycle management and concurrent operations. Security teams should conduct thorough vulnerability assessments to identify systems running affected kernel versions and implement comprehensive patch management procedures to ensure timely remediation across all operational environments.