CVE-2026-68392: Linux Kernel Use-After-Free Vulnerability

CVE-2026-68392 Overview

CVE-2026-68392 is a use-after-free (UAF) vulnerability in the Linux kernel Bluetooth management (mgmt) subsystem. The flaw resides in the unpair_device and disconnect_sync code paths, where RCU-protected pointers are dereferenced outside of RCU read-side critical sections. This improper synchronization allows the hci_conn object to be freed while still in use, resulting in a use-after-free condition. Local authenticated attackers with the ability to interact with the Bluetooth stack can trigger the flaw to compromise kernel memory integrity, leading to potential privilege escalation or denial of service.

Critical Impact
Local exploitation of this Bluetooth mgmt UAF can corrupt kernel memory, enabling privilege escalation, information disclosure, or system crash.

Affected Products

Linux kernel Bluetooth subsystem (net/bluetooth/mgmt.c)
Distributions shipping affected upstream kernel versions prior to the referenced stable commits
Systems with Bluetooth hardware and the mgmt interface enabled

Discovery Timeline

2026-08-10 - CVE-2026-68392 published to NVD
2026-08-13 - Last updated in NVD database

Technical Details for CVE-2026-68392

Vulnerability Analysis

The vulnerability originates in the Linux kernel Bluetooth mgmt subsystem, specifically within the unpair_device and disconnect_sync functions. These functions look up an hci_conn connection structure and subsequently invoke hci_abort_conn() on the returned pointer. The lookup relies on Read-Copy-Update (RCU) pointer semantics, which require callers to hold an RCU read-side lock while dereferencing the protected pointer.

The original code dereferences these RCU-protected pointers outside of a valid RCU critical section. Because the hci_conn object can be freed concurrently by another kernel thread, the pointer can become stale before it is used. Any subsequent access to the freed object constitutes a use-after-free.

The upstream fix replaces the RCU-based lookup with acquisition of hdev->lock before performing hci_conn lookup and calling hci_abort_conn(). This guarantees that the connection object is fully initialized and not concurrently freed during the operation.

Root Cause

The root cause is improper synchronization when accessing RCU-protected data structures in the Bluetooth mgmt code path. Dereferencing an RCU-protected hci_conn pointer without holding rcu_read_lock() or an equivalent mutex allows the object lifetime to overlap with concurrent teardown, producing a use-after-free (CWE-416).

Attack Vector

Exploitation requires local access with low privileges and the ability to invoke Bluetooth management operations. An attacker races unpair or disconnect operations against connection teardown to trigger the dangling hci_conn dereference. Successful exploitation may corrupt kernel heap memory, enabling privilege escalation or causing a kernel panic. No user interaction is required, and the impact spans confidentiality, integrity, and availability.

No public proof-of-concept exploit is available at the time of publication. Technical detail is available in the upstream stable commits, including 16cd6644, 579faba5, and b1151100.

Detection Methods for CVE-2026-68392

Indicators of Compromise

Kernel oops or panic messages referencing hci_abort_conn, unpair_device, or disconnect_sync in dmesg
KASAN reports flagging use-after-free in net/bluetooth/mgmt.c or hci_conn structures
Unexpected Bluetooth service restarts or bluetoothd crashes coinciding with device pair/unpair activity

Detection Strategies

Enable CONFIG_KASAN on test kernels to catch UAF conditions in the Bluetooth stack during fuzzing or QA
Monitor kernel ring buffer logs via journalctl -k for RCU stalls, slab-out-of-bounds, or UAF warnings tied to Bluetooth modules
Correlate local user activity with abnormal Bluetooth mgmt socket usage patterns

Monitoring Recommendations

Alert on kernel crash telemetry that references hci_conn, bluetooth, or mgmt symbols
Track kernel package versions across the fleet and flag hosts running unpatched Linux kernels with Bluetooth enabled
Log and review unprivileged user access to /dev/rfkill and Bluetooth mgmt sockets

How to Mitigate CVE-2026-68392

Immediate Actions Required

Apply the upstream Linux kernel patch series that replaces RCU-based hci_conn lookup with hdev->lock in unpair_device and disconnect_sync
Update to a distribution kernel that has backported the fix from the referenced stable branches
On systems that do not require Bluetooth, disable the bluetooth kernel module and stop bluetoothd

Patch Information

The fix is available in the mainline and stable Linux kernel trees. Relevant commits include 16cd66443957, 579faba5ede6, 8bc83f9ef678, b11511006f9e, and ca58ad287bfc. Consult your distribution vendor for backported package availability.

Workarounds

Disable the Bluetooth stack on systems that do not require it by blacklisting the bluetooth and btusb modules
Restrict access to Bluetooth mgmt operations to trusted administrative users only
Physically disable Bluetooth radios on hosts where the feature is not needed

bash

# Configuration example: disable Bluetooth kernel modules
echo 'install bluetooth /bin/true' | sudo tee /etc/modprobe.d/disable-bluetooth.conf
echo 'install btusb /bin/true'     | sudo tee -a /etc/modprobe.d/disable-bluetooth.conf
sudo systemctl disable --now bluetooth.service
sudo rmmod btusb bluetooth 2>/dev/null || true