Cloudanix VulnDB

CVE-2026-64233

Medium · 5.5

CVSS

5.5

EPSS

0.1%

Published

Jul 24, 2026

CISA due date

—

Cloudanix analysis

Schedule a fix SSVC: Track

A flaw in the Linux kernel's USB video gadget code can let a privileged local program crash the system by racing two operations that should not happen at the same time.

Exploitation
Local Privilege
Attacker needs
Low Privilege
Complexity
Moderate
Impact
Denial Of Service
Component
OS kernel
Class
Race Condition
Remediation
Patch
Effort
Medium
Patch risk
Low

What it actually does

Race condition during uvc_function_bind() allows concurrent uvcg_extension_drop() to free a struct uvcg_extension while the bind path walks the extension_units list without holding opts->lock, resulting in use-after-free dereference.

Why it matters to the business

May cause kernel crashes or denial of service on Linux systems exposing USB gadget UVC functions via configfs; limited to environments where untrusted privileged processes can mount configfs and bind gadgets.

How an attack unfolds

A privileged local process mounts configfs, creates a gadget UVC function with extension units, then concurrently issues rmdir on an extensions subdir while writing the UDC name to trigger bind; the unsynchronized list walk in uvc_function_bind dereferences the freed object.

How to fix it

Apply the upstream fix that acquires opts->lock before the XU string-descriptor fixup and releases it after the final uvc_copy_descriptors call (via the new error_unlock label). Rebuild and deploy the patched kernel; no fixed version tags are listed so track the commit that resolves the unsynchronized XU list walks.

How to confirm the fix worked

Confirm the patched kernel source contains the opts->lock acquisition around the XU walks in uvc_function_bind and the error_unlock label; test by exercising concurrent configfs rmdir and UDC bind under the gadget UVC function.

Typical attack path

  1. Mount configfs and create UVC gadget function with extension units
  2. Open the gadget directory and prepare concurrent rmdir of an extensions subdir
  3. Write the UDC name to the gadget to invoke uvc_function_bind while the rmdir races
  4. Trigger list walk that dereferences the freed uvcg_extension object

How to detect it

Inspect kernel logs for oops or panic messages referencing uvc_function_bind, uvcg_extension, or extension_units list operations; correlate with audit logs showing concurrent configfs rmdir and gadget UDC writes by privileged processes.

What your security team should do

  • Prioritize patching Linux kernels that expose USB gadget UVC functions via configfs
  • Restrict configfs mounts and gadget UDC writes to trusted processes only
  • Monitor for kernel oops or crashes involving uvcg_extension or uvc_function_bind
  • Audit any custom gadget configuration scripts that manipulate extension units

The record

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: uvc: hold opts->lock across XU walks in uvc_function_bind uvc_function_bind() walks &opts->extension_units twice without holding opts->lock: - directly, for the iExtension string-descriptor fixup loop; - indirectly, four times via uvc_copy_descriptors() (once per speed), where the helper iterates uvc->desc.extension_units (which aliases &opts->extension_units) to size and emit XU descriptors. The configfs side (uvcg_extension_make / uvcg_extension_drop, in drivers/usb/gadget/function/uvc_configfs.c) takes opts->lock around its list_add_tail / list_del operations. A privileged userspace process that holds the configfs subtree open and writes the gadget UDC name to bind the function while concurrently rmdir()'ing an extensions subdir can race uvcg_extension_drop() against the bind-time list walks and dereference a freed struct uvcg_extension. Hold opts->lock from the start of the XU string-descriptor fixup through the last uvc_copy_descriptors() call, releasing on the descriptor-error path via a new error_unlock label that drops the lock before falling through to the existing error label. This matches the locking discipline of the configfs callbacks and removes the only remaining unsynchronised reader of the XU list during bind. Reachability: only privileged processes that can mount configfs and write to gadget UDC files can trigger the race, so this is a correctness fix rather than a security boundary.

Affected packages

Ecosystem Package Introduced Fixed