CVE-2026-80764 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_event: fix LE list UAF on reset
hci_cc_reset() clears the LE accept and resolving lists without taking hdev->lock. Other command-complete handlers serialize updates to these lists with that lock, and the debugfs readers hold it while walking them.
This permits the reset completion and a debugfs read to interleave as follows:
hci_rx_work debugfs reader ----------- -------------- lock hdev->lock fetch current entry list_del(entry) kfree(entry) read entry fields
The reader then dereferences a freed list entry and may follow its stale next pointer.
KASAN reported:
BUG: KASAN: slab-use-after-free in white_list_show+0x15f/0x180 Read of size 1 at addr ffff8881015dab16 by task poc/95
Call Trace: white_list_show+0x15f/0x180 seq_read_iter+0x3ff/0x1190 seq_read+0x267/0x3d0 vfs_read+0x177/0xa20 ksys_read+0xf7/0x1c0
Allocated by task 91: hci_bdaddr_list_add+0x1a6/0x3a0 hci_cc_le_add_to_accept_list+0xab/0x140 hci_cmd_complete_evt+0x26c/0x9a0 hci_event_packet+0x454/0xb20 hci_rx_work+0x293/0x730
Freed by task 90: kfree+0x131/0x3c0 hci_bdaddr_list_clear+0xd8/0x160 hci_cc_reset+0x28a/0x370 hci_cmd_complete_evt+0x26c/0x9a0 hci_event_packet+0x454/0xb20 hci_rx_work+0x293/0x730
Take hdev->lock around both list clears. This matches the existing mutation and traversal locking convention.
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Analysis
by VulDB Data Team • 09/04/2026
The Linux kernel Bluetooth subsystem contains a critical synchronization flaw within the HCI event handling logic, specifically involving the LE (Low Energy) address lists used for filtering incoming connections. The vulnerability arises in the hci_cc_reset function, which is responsible for clearing the LE accept and resolving lists when a device reset command completes. This operation was performed without acquiring the necessary hdev->lock mutex that protects these data structures. In contrast, other command-complete handlers that modify these lists correctly serialize their updates using this lock, and debugfs readers that traverse the lists also hold the lock to ensure safe access during iteration. The absence of locking in the reset handler creates a race condition where the list modification can interleave with concurrent read operations from userspace via debugfs interfaces.
This concurrency issue manifests as a use-after-free vulnerability, classified under CWE-416. When hci_cc_reset executes, it calls kfree to deallocate individual entries within the LE lists while they are still being traversed by a debugfs reader thread that holds no lock protection for this specific critical section. The sequence of events allows the reset handler to delete and free a list entry immediately after the reader has fetched its current pointer but before the reader finishes accessing the entry's fields or following its next pointer. Consequently, the reader dereferences memory that has already been returned to the kernel slab allocator, leading to undefined behavior. This can result in data corruption, system crashes, or potentially arbitrary code execution if an attacker can control the contents of the freed memory and trigger the race condition reliably.
The operational impact is significant as it affects local attackers who have access to debugfs interfaces, which are typically available on development kernels or systems where debugging tools are enabled without sufficient restrictions. The KASAN report confirms a slab-use-after-free error in white_list_show, indicating that the kernel detected an invalid read from freed memory. Such vulnerabilities undermine system stability and security integrity by allowing potential exploitation of race conditions to bypass access controls or crash the Bluetooth stack, which could lead to denial-of-service against network services relying on Bluetooth connectivity.
To mitigate this vulnerability, developers must ensure that all modifications to shared data structures are properly synchronized with concurrent readers. The fix involves wrapping both list clear operations in hci_cc_reset with a call to acquire and release hdev->lock. This aligns the reset handler's behavior with the existing locking conventions used by other command-complete handlers and debugfs traversal code, ensuring mutual exclusion between writers and readers of the LE address lists. System administrators should apply kernel updates that include this patch immediately if they expose Bluetooth debug interfaces to untrusted users or run in environments where local privilege escalation is a concern. Adhering strictly to locking protocols for shared resources prevents race conditions and maintains memory safety within the kernel space, aligning with best practices outlined in ATT&CK techniques related to exploitation of software vulnerabilities during system operations.