Cloudanix VulnDB

CVE-2026-98756

None

CVSS

—

EPSS

0.2%

Published

Oct 18, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A timing issue in how a USB controller driver loads on some computers can cause the whole system to crash during startup.

Exploitation
Local Privilege
Attacker needs
Local User
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 PCI function probing of Cadence USBSS controller allows second function probe to call pci_get_drvdata() before first function has stored driver data, resulting in NULL dereference and kernel panic in cdns3_pci_probe.

Why it matters to the business

Kernel crashes during system boot or USB driver initialization on affected hardware can cause denial of service and unexpected downtime, though low EPSS and absence from KEV indicate limited real-world exploitation risk five days after disclosure.

How an attack unfolds

An attacker with local access or ability to influence PCI device enumeration timing triggers the window where the second function probes while the first has pci_is_enabled() true but has not yet called pci_set_drvdata(); this leads directly to the NULL dereference without requiring crafted input beyond normal driver loading.

How to fix it

Apply the upstream fix that returns -EPROBE_DEFER when pci_get_drvdata() is NULL; update to a Linux kernel containing the resolution for CVE-2026-98756 once released by the distribution.

How to confirm the fix worked

Confirm kernel source contains the EPROBE_DEFER return in cdns3_pci_probe; verify no NULL dereference occurs under concurrent function probing by reviewing dmesg after repeated driver reloads or boot sequences on affected hardware.

Typical attack path

  1. Trigger PCI device probe sequence for Cadence USBSS two-function controller
  2. Ensure second function reaches cdns3_pci_probe while first function is between pci_is_enabled() check and pci_set_drvdata()
  3. pci_get_drvdata() returns NULL
  4. NULL pointer dereference on wrap->devfn assignment crashes kernel

How to detect it

Search kernel logs and crash dumps for the call trace containing cdns3_pci_probe, local_pci_probe, pci_device_probe and the NULL dereference; correlate with PCI device enumeration events around driver initialization.

  • cdns3_pci_probe+0xa4/0x300
  • pci_get_drvdata returns NULL before devfn assignment
  • Call trace ending in ret_from_fork after cdns3_pci_driver_init

What your security team should do

  • Monitor kernel update channels for the patch and schedule deployment within normal maintenance windows given low EPSS
  • Add cdns3_pci_probe and related probe functions to kernel oops monitoring rules
  • Test boot stability on systems with Cadence USBSS controllers before and after updates

The record

In the Linux kernel, the following vulnerability has been resolved: usb: cdns3: Fix NULL pointer dereference in cdns3_pci_probe The Cadence USBSS controller is a two-function PCI device. The first probed function allocates the driver data and stores it with pci_set_drvdata(), while the second function reuses it via pci_get_drvdata() when pci_is_enabled() reports that the first function has already been probed. When the second function is probed while the first one has been enabled but has not yet set its driver data, pci_get_drvdata() returns NULL, and the subsequent wrap->devfn assignment dereferences a NULL pointer and crashes the kernel. logs: Call trace: cdns3_pci_probe+0xa4/0x300 local_pci_probe+0x44/0xa8 pci_call_probe+0x54/0x158 pci_device_probe+0x84/0x100 really_probe+0x184/0x3d0 __driver_probe_device+0x80/0x178 driver_probe_device+0x44/0xe8 __driver_attach+0xec/0x1f8 bus_for_each_dev+0x7c/0xe0 driver_attach+0x28/0x38 bus_add_driver+0x110/0x238 driver_register+0x64/0x128 __pci_register_driver+0x50/0x60 cdns3_pci_driver_init+0x28/0x38 do_one_initcall+0x5c/0x280 do_initcalls+0x104/0x1d8 kernel_init_freeable+0x140/0x218 kernel_init+0x28/0x1f8 ret_from_fork+0x10/0x20 Return -EPROBE_DEFER in this case so that probing is retried after the first function has completed its probe.

Affected packages

Ecosystem Package Introduced Fixed