CVE-2026-68227 Overview
CVE-2026-68227 is a memory leak vulnerability in the Linux kernel cx231xx media USB driver. The flaw stems from incorrect device-managed resource (devres) lifetime handling. USB drivers bind to USB interfaces, but the affected driver tied managed resources to the parent USB device rather than the interface itself. As a result, driver state is not released when the driver is unbound without a physical disconnect, such as during probe deferral or USB configuration changes. The kernel maintainers have merged a fix that ensures driver state is released on driver unbind.
Critical Impact
Repeated bind and unbind cycles of the cx231xx USB media driver leak kernel memory, degrading system stability on hosts that use Conexant cx231xx-based capture devices.
Affected Products
- Linux kernel media: cx231xx USB driver
- Systems using Conexant cx231xx-based USB video capture hardware
- Kernel branches referenced by the upstream stable commits 7d6358a, a373f1a, c5ccb01e, e797e25, and f468b7ee
Discovery Timeline
- 2026-08-10 - CVE-2026-68227 published to NVD
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-68227
Vulnerability Analysis
The Linux kernel provides device-managed resource helpers (devres) that automatically free allocations when a device is removed. The correct pattern for USB drivers is to attach these resources to the struct usb_interface the driver binds to. The cx231xx driver instead tied managed resources to the parent struct usb_device. Parent USB devices persist across driver unbind events, so resources associated with them are only released on physical disconnect.
This lifetime mismatch causes driver state to remain allocated after the driver is unbound. Common triggers include probe deferral, manual unbind through sysfs, module reload, and USB configuration changes. Each cycle leaks the driver's private state.
Root Cause
The root cause is an incorrect device pointer passed to devres allocation routines inside the cx231xx driver. Because the parent USB device outlives the interface binding, devres never fires the release callbacks at unbind time. The upstream fix rebinds the resource lifetime to the USB interface so the kernel releases state during disconnect or driver unbind.
Attack Vector
This is a local reliability and resource-exhaustion issue rather than a remote code execution flaw. An attacker or unprivileged workflow that can repeatedly trigger bind and unbind operations, for example by toggling module load state or forcing probe deferral, can grow kernel memory usage until the system degrades. Physical access with a cx231xx-based USB device increases exposure but is not required to reproduce the leak on a system where the driver loads.
No verified proof-of-concept code is published. Refer to the upstream commits linked below for the patch content.
Detection Methods for CVE-2026-68227
Indicators of Compromise
- Growth in kernel kmalloc slab caches used by the cx231xx driver across bind and unbind cycles
- dmesg entries showing repeated cx231xx probe, unbind, or probe-deferral events without matching disconnect messages
- Steady decline in MemAvailable on hosts that host cx231xx-based USB capture devices under long uptime
Detection Strategies
- Compare installed kernel package versions against the fixed commits 7d6358a, a373f1a, c5ccb01e, e797e25, and f468b7ee to confirm patch status.
- Instrument kmemleak on test systems that exercise the cx231xx driver bind and unbind path to observe unreleased allocations.
- Query endpoint telemetry for module load, unload, and sysfs unbind events targeting cx231xx on production hosts.
Monitoring Recommendations
- Track kernel memory metrics such as Slab, SReclaimable, and SUnreclaim from /proc/meminfo on hosts with cx231xx hardware.
- Alert on repeated modprobe cx231xx or echo ... > /sys/bus/usb/drivers/cx231xx/unbind operations from non-administrative contexts.
- Forward kernel logs to a centralized platform and alert on abnormal driver bind churn.
How to Mitigate CVE-2026-68227
Immediate Actions Required
- Update to a Linux kernel build that includes one of the upstream fixes: Kernel Git Commit 7d6358a, Kernel Git Commit a373f1a, Kernel Git Commit c5ccb01e, Kernel Git Commit e797e25, or Kernel Git Commit f468b7ee.
- Inventory hosts loading the cx231xx module and prioritize patching those with long uptime or exposed USB ports.
- Reboot affected systems after patching to release any leaked state accumulated before the update.
Patch Information
The fix reassigns device-managed resource lifetime in the cx231xx driver from the parent USB device to the bound USB interface, ensuring devres release callbacks run at driver unbind. Distributions ship the fix through their standard stable-kernel update channels. Apply vendor kernel updates that reference the commits listed above.
Workarounds
- Blacklist the cx231xx module on systems that do not require Conexant USB capture hardware by adding blacklist cx231xx to /etc/modprobe.d/.
- Avoid repeated manual bind and unbind operations against the cx231xx driver on unpatched hosts.
- Restrict physical USB port access on systems where kernel updates cannot be applied immediately.
# Verify kernel version and confirm the cx231xx module is not loaded on unpatched hosts
uname -r
lsmod | grep cx231xx
echo 'blacklist cx231xx' | sudo tee /etc/modprobe.d/cx231xx-blacklist.conf
sudo update-initramfs -u
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
