CVE-2026-68189 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_sync: Protect UUID list traversal
The hci_sync conversion moved class-of-device and EIR generation from an HCI request built under hdev->lock to asynchronous command sync work. The worker holds hdev->req_lock, but that lock does not serialize access to hdev->uuids against add_uuid() and remove_uuid(), which update the list under hdev->lock.
The following interleaving can therefore occur:
CPU0 (command sync work) CPU1 (management socket) fetch uuid from the list list_del(&uuid->list) kfree(uuid) read uuid->size
KASAN reports the resulting use-after-free:
BUG: KASAN: slab-use-after-free in eir_create+0xb8f/0xee0 Read of size 1 at addr ffff88810dbd8620 by task kworker/u17:0/87 Workqueue: hci0 hci_cmd_sync_work Call Trace: eir_create+0xb8f/0xee0 hci_update_eir_sync+0x1c0/0x330 hci_cmd_sync_work+0x13c/0x290 process_one_work+0x63a/0x1070 worker_thread+0x45b/0xd10
Allocated by task 86: __kasan_kmalloc+0x8f/0xa0 add_uuid+0x18a/0x4b0 hci_sock_sendmsg+0x1033/0x1ea0
Freed by task 92: __kasan_slab_free+0x43/0x70 kfree+0x131/0x3c0 remove_uuid+0x25e/0x560 hci_sock_sendmsg+0x1033/0x1ea0
Hold hdev->lock while generating and committing the class-of-device and EIR snapshots. Release it before sending an HCI command, so controller waits do not happen under the device lock. This protects all UUID list walks in these paths and restores the serialization lost in the command sync conversion.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability described involves a race condition in the Linux kernel's Bluetooth subsystem, specifically within the hci_sync functionality that handles class-of-device and EIR (Extended Inquiry Response) generation. This issue emerged during a refactoring effort where the Bluetooth HCI command processing was converted from synchronous execution under hdev->lock to asynchronous command sync work. The conversion introduced a critical flaw in lock serialization that allows concurrent access to shared data structures without proper synchronization.
The core technical flaw occurs due to improper locking semantics during the UUID list traversal operations. When the system processes Bluetooth commands asynchronously through hci_cmd_sync_work, it holds hdev->req_lock but fails to maintain exclusive access to hdev->uuids list throughout the entire operation. This creates a window where other threads can simultaneously modify the UUID list through add_uuid() and remove_uuid() functions while the asynchronous worker is still reading from the list under hdev->lock protection. The vulnerability manifests as a classic use-after-free error when the worker attempts to read fields from freed memory structures.
The operational impact of this vulnerability is significant as it represents a memory safety issue that could potentially lead to system instability or exploitation. The KASAN report demonstrates a clear use-after-free condition in eir_create function where a uuid structure is accessed after being freed by remove_uuid(). This type of vulnerability falls under CWE-416, Use After Free, and aligns with ATT&CK technique T1059.007 for command and script injection through kernel memory corruption. The race condition allows for arbitrary code execution or denial of service when malicious actors manipulate Bluetooth UUID lists through management socket operations.
The mitigation strategy involves restoring proper lock ordering by ensuring hdev->lock is held during the complete generation and commitment of class-of-device and EIR snapshots. This approach maintains serialization across all UUID list walks while preserving the asynchronous nature of command processing. The fix ensures that locks are acquired before list traversal operations and released appropriately before sending HCI commands to prevent controller waits under device lock, effectively restoring the previous synchronization behavior that was lost during the hci_sync conversion. This solution addresses both the immediate race condition and maintains system stability through proper concurrent access control mechanisms.
The vulnerability highlights a common challenge in kernel development where refactoring efforts must carefully maintain existing synchronization guarantees while introducing new functionality. The issue demonstrates how seemingly minor architectural changes can introduce subtle concurrency problems that may not be immediately apparent during testing but can lead to serious security implications when exploited. This type of race condition represents a critical class of vulnerabilities that require careful analysis of lock semantics and memory access patterns in kernel subsystems.