CVE-2026-98008
Received Received - Intake

NULL Pointer Dereference in Linux Kernel macb Driver

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net: macb: fix NULL pointer dereference on unbind with fixed-link When the device tree describes a fixed-link and has no "mdio" child node, macb_mii_init() returns early without allocating the MDIO bus, leaving bp->mii_bus as NULL. Two cleanup paths then dereference this NULL bus: 1. On driver unbind, macb_remove() unconditionally calls mdiobus_unregister(bp->mii_bus), which oopses: Unable to handle kernel NULL pointer dereference at virtual address 00000000000004a8 pc : mdiobus_unregister+0x14/0xa4 lr : macb_remove+0x38/0xa4 Call trace: mdiobus_unregister+0x14/0xa4 (P) macb_remove+0x38/0xa4 platform_remove+0x20/0x30 device_release_driver_internal+0x1c8/0x224 unbind_store+0xb4/0xbc 2. On the probe error path in macb_probe(), reached when macb_mii_init() has succeeded but a subsequent step fails, the err_out_unregister_mdio label runs the same unconditional cleanup. mdiobus_unregister() and mdiobus_free() do not guard against a NULL bus, so guard the calls in both macb_remove() and the probe error path.

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-98008
EUVD
EUVD-2026-86661

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a NULL pointer dereference vulnerability in the Linux kernel's macb network driver. It occurs when the device tree has a fixed-link without an MDIO child node, causing macb_mii_init() to return early without allocating the MDIO bus. This leaves bp->mii_bus as NULL, which is later dereferenced during driver unbind or probe error handling, leading to a kernel oops.

Detection Guidance

This vulnerability is specific to the Linux kernel's macb network driver and involves a NULL pointer dereference during device unbind or probe failure. Detection requires checking kernel logs for crashes related to macb or mdiobus operations. Look for messages like 'Unable to handle kernel NULL pointer dereference' in dmesg or system logs.

Impact Analysis

This vulnerability can cause system crashes (kernel oops) when unloading the macb driver or during probe failures. It may lead to denial of service if the affected network interface is critical for system operations.

Mitigation Strategies

Apply the latest kernel patches from your Linux distribution to fix the macb driver issue. If using a fixed-link device tree configuration without an MDIO child node, ensure the driver is updated to handle NULL mii_bus safely. Monitor kernel updates for CVE-2026-98008 fixes.

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