CVE-2026-64471 Overview
CVE-2026-64471 is a use-after-free vulnerability in the Linux kernel's Bluetooth USB driver (btusb). The flaw occurs when Bluetooth controller registration fails and the driver does not properly release sibling USB interfaces. When those interfaces are later disconnected, the kernel accesses freed memory, leading to use-after-free and double-free conditions. The issue was reported by a reviewer named Sashiko while auditing a fix for a wakeup source leak in the btusb probe error paths. The Linux kernel maintainers have released patches across multiple stable branches.
Critical Impact
Use-after-free and double-free conditions in kernel space can lead to memory corruption, kernel crashes, and potentially local privilege escalation on systems with vulnerable Bluetooth USB adapters.
Affected Products
- Linux kernel (mainline and stable branches shipping the btusb driver)
- Linux distributions bundling affected kernel versions with Bluetooth USB support
- Systems using USB-attached Bluetooth controllers relying on the drivers/bluetooth/btusb.c module
Discovery Timeline
- 2026-07-25 - CVE-2026-64471 published to NVD
- 2026-07-25 - Last updated in NVD database
Technical Details for CVE-2026-64471
Vulnerability Analysis
The vulnerability resides in the btusb driver, which manages USB-attached Bluetooth controllers in the Linux kernel. During probe, btusb binds to multiple sibling USB interfaces exposed by a single Bluetooth device. When the controller registration step fails after these sibling interfaces have been claimed, the error path does not release them. The associated interface data structures remain referenced by the USB core even though the driver has torn down its controller state.
When the USB device is subsequently disconnected, the kernel invokes the driver's disconnect handler on the stale sibling interfaces. This triggers access to memory that was already freed during the failed registration cleanup, producing a use-after-free. In some scenarios the same object is released a second time, producing a double-free.
Root Cause
The root cause is incomplete cleanup in the btusb probe error path. The driver claims sibling interfaces before calling controller registration but omits the reverse release step when registration returns an error. This asymmetry leaves interface references in an inconsistent state relative to the driver's private data lifetime.
Attack Vector
Exploitation requires physical or administrative interaction with USB Bluetooth hardware, or a scenario in which controller registration reliably fails such as constrained resources or a malicious USB device. An attacker who can induce registration failure and then trigger a disconnect can corrupt kernel memory. See the Linux kernel commit references for patch details, including commit e6313b8 and commit da7d775.
Detection Methods for CVE-2026-64471
Indicators of Compromise
- Kernel oops or panic traces originating in btusb_disconnect or related USB Bluetooth interface teardown paths
- KASAN (Kernel Address Sanitizer) reports flagging use-after-free or double-free in the btusb module
- Repeated hci registration failures in dmesg followed by disconnect-time crashes
Detection Strategies
- Monitor kernel logs for btusb probe failures accompanied by subsequent disconnect faults on the same USB bus address
- Enable KASAN in test and staging environments running kernels with the btusb driver to surface latent memory errors
- Track kernel version inventory to identify hosts running unpatched builds that include drivers/bluetooth/btusb.c
Monitoring Recommendations
- Forward dmesg and journald kernel messages to a centralized logging platform and alert on btusb error patterns
- Correlate USB device connect and disconnect events with kernel fault traces to detect exploitation attempts
- Audit systems that expose USB ports to untrusted users, such as kiosks and shared workstations
How to Mitigate CVE-2026-64471
Immediate Actions Required
- Apply the latest stable kernel update from your Linux distribution that includes the btusb sibling interface release fix
- On systems that do not require Bluetooth, blacklist or unload the btusb and bluetooth kernel modules
- Restrict physical USB access on high-value hosts to reduce the attack surface for USB-triggered kernel bugs
Patch Information
The fix has been backported across multiple Linux stable branches. Refer to the upstream commits: 14e02f1, 1ce5012, 468fcdf, 8db0ce3, da7d775, e09ac7d, e6313b8, and eedc686. Deploy the vendor-provided kernel package that incorporates these commits.
Workarounds
- Disable Bluetooth in firmware or via kernel command line (modprobe.blacklist=btusb) on systems that do not require it
- Physically remove or disable USB Bluetooth dongles on servers where Bluetooth is not a functional requirement
- Apply USB device filtering policies through tools such as USBGuard to allow only trusted Bluetooth controllers
# Blacklist the btusb module until a patched kernel is deployed
echo "blacklist btusb" | sudo tee /etc/modprobe.d/blacklist-btusb.conf
sudo modprobe -r btusb
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
