CVE-2026-63927: Linux Kernel DWC2 Use-After-Free Flaw

CVE-2026-63927 Overview

CVE-2026-63927 is a use-after-free vulnerability in the Linux kernel's dwc2 USB host controller driver. The flaw exists in debug code that dereferences the urb (USB Request Block) pointer after calling usb_hcd_giveback_urb(). Once usb_hcd_giveback_urb() returns, the URB memory may be reclaimed, making any subsequent access to urb->status a use-after-free condition. A local attacker with the ability to trigger USB transfer completion paths can exploit this flaw to corrupt kernel memory, potentially leading to privilege escalation or denial of service.

Critical Impact
Local attackers can leverage the use-after-free condition in the dwc2 driver to compromise kernel memory integrity, with potential impact on confidentiality, integrity, and availability of affected Linux systems.

Affected Products

Linux kernel builds including the dwc2 USB host controller driver
Stable kernel branches prior to the commits listed in the upstream fix references
Embedded and ARM-based Linux platforms that rely on the DesignWare USB 2.0 controller

Discovery Timeline

2026-07-19 - CVE-2026-63927 published to NVD
2026-07-20 - Last updated in NVD database

Technical Details for CVE-2026-63927

Vulnerability Analysis

The vulnerability resides in the Linux kernel's dwc2 USB host controller driver, specifically in debug-related code paths that handle URB completion. When a USB transfer completes, the driver calls usb_hcd_giveback_urb() to return the URB to its owner. After this call, the URB structure is no longer safe to reference because the USB core or the completing driver may free the allocation. The vulnerable code then dereferences urb->status, resulting in a use-after-free [CWE-416].

An attacker with local access can trigger this code path by initiating or completing USB transactions through the affected controller. Exploitation requires low privileges and no user interaction, and the impact spans confidentiality, integrity, and availability.

Root Cause

The root cause is improper ordering of operations in the URB completion path. The debug code reads urb->status after usb_hcd_giveback_urb() has already relinquished ownership of the URB. The upstream patch resolves the issue by saving urb->status to a local variable before calling usb_hcd_giveback_urb(), ensuring the value is captured while the URB is still valid.

Attack Vector

Exploitation requires local access to a system with the dwc2 driver loaded and an active USB host controller. An attacker with the ability to interact with USB endpoints or trigger USB transfer completions can drive the vulnerable code path. Successful exploitation of the freed URB memory can enable kernel memory corruption, which skilled attackers can weaponize for privilege escalation.

No public proof-of-concept exploit code has been published. The vulnerability is described in prose only; refer to the upstream kernel commits linked in the references for the exact fix.

Detection Methods for CVE-2026-63927

Indicators of Compromise

Kernel oops or panic messages referencing dwc2 functions or usb_hcd_giveback_urb in dmesg or /var/log/kern.log
KASAN (Kernel Address Sanitizer) reports flagging use-after-free access in the dwc2 URB completion path
Unexpected USB host controller resets or driver reinitialization events on systems using the DesignWare USB 2.0 IP

Detection Strategies

Enable CONFIG_KASAN on test kernels to surface use-after-free access in the dwc2 completion path during fuzzing and QA cycles
Audit installed kernel versions against the fixed commits (0584af4, 63b0daf, 84ea928, d5fc183) to identify unpatched hosts
Correlate USB subsystem crash traces with process context using EDR telemetry to identify local exploitation attempts

Monitoring Recommendations

Aggregate kernel logs centrally and alert on repeated dwc2 warnings or oops signatures
Track loaded kernel module versions across the fleet and flag hosts running vulnerable dwc2 builds
Monitor for unexpected local privilege escalations following USB device activity on embedded and ARM Linux endpoints

How to Mitigate CVE-2026-63927

Immediate Actions Required

Apply the upstream Linux kernel patches referenced in the NVD entry and rebuild or update affected kernels
Prioritize patching on embedded, ARM, and IoT devices that ship with the dwc2 driver enabled by default
Restrict local and physical access to systems until the fixed kernel is deployed

Patch Information

The fix is committed to the mainline and stable Linux kernel trees. The relevant commits include 0584af4fe40f, 63b0dafa676a, 6d0b79d1d111, 84ea928ed584, 9ea06a3fbf9f, 9fe1d84f7e2c, a15eeeceb94c, and d5fc183ed614. Distribution vendors will backport these commits into their supported kernel packages. Update through your Linux distribution's package manager once the patched kernel is available.

Workarounds

Unload or blacklist the dwc2 module on systems that do not require the DesignWare USB 2.0 host controller
Disable kernel debug options that exercise the vulnerable code path where feasible
Enforce strict local user access controls and disable untrusted USB peripherals on affected hosts

bash

# Verify kernel version and check for the dwc2 module
uname -r
lsmod | grep dwc2

# Temporarily unload the dwc2 driver (only if the controller is not required)
sudo modprobe -r dwc2

# Persistently blacklist the module until the patched kernel is applied
echo "blacklist dwc2" | sudo tee /etc/modprobe.d/blacklist-dwc2.conf
sudo update-initramfs -u