# CVE-2026-98008: net: macb: fix NULL pointer dereference on unbind with fixed-link

> A local attacker with high privileges can cause a kernel crash by unbinding a network driver configured with a fixed-link and no MDIO node.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104673, BELL-CVE-2026-98008, DEBIAN-CVE-2026-98008, GHSA-h4xg-972w-f7c3, UBUNTU-CVE-2026-98008

## What is CVE-2026-98008?

CVE-2026-98008 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2026-98008?


## How do I fix CVE-2026-98008?

Apply the vendor's patch.

## Is CVE-2026-98008 being exploited?

There is no known exploitation of CVE-2026-98008 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98008 and fix it if it is affected.

What it is: CVE-2026-98008 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98008 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98008/ (Markdown: https://insights.sbomify.com/CVE-2026-98008/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98008
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98008
- OSV: https://osv.dev/vulnerability/CVE-2026-98008

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98008/
Summaries are generated and may contain mistakes; the official description above is the record.