# CVE-2024-49998: net: dsa: improve shutdown sequence

> A race condition and null pointer dereference in the Linux kernel DSA subsystem can cause a system crash during network interface shutdown.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Oct 2024
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-51966, AZL-51998, BELL-CVE-2024-49998, DEBIAN-CVE-2024-49998, GHSA-3xm8-389p-x4rm, ROOT-OS-DEBIAN-12-CVE-2024-49998, UBUNTU-CVE-2024-49998

## What is CVE-2024-49998?

CVE-2024-49998 is a medium-severity vulnerability in Linux kernel, published on 21 Oct 2024. 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: dsa: improve shutdown sequence

Alexander Sverdlin presents 2 problems during shutdown with the
lan9303 driver. One is specific to lan9303 and the other just happens
to reproduce there.

The first problem is that lan9303 is unique among DSA drivers in that it
calls dev_get_drvdata() at "arbitrary runtime" (not probe, not shutdown,
not remove):

phy_state_machine()
-> ...
   -> dsa_user_phy_read()
      -> ds->ops->phy_read()
         -> lan9303_phy_read()
            -> chip->ops->phy_read()
               -> lan9303_mdio_phy_read()
                  -> dev_get_drvdata()

But we never stop the phy_state_machine(), so it may continue to run
after dsa_switch_shutdown(). Our common pattern in all DSA drivers is
to set drvdata to NULL to suppress the remove() method that may come
afterwards. But in this case it will result in an NPD.

The second problem is that the way in which we set
dp->conduit->dsa_ptr = NULL; is concurrent with receive packet
processing. dsa_switch_rcv() checks once whether dev->dsa_ptr is NULL,
but afterwards, rather than continuing to use that non-NULL value,
dev->dsa_ptr is dereferenced again and again without NULL checks:
dsa_conduit_find_user() and many other places. In between dereferences,
there is no locking to ensure that what was valid once continues to be
valid.

Both problems have the common aspect that closing the conduit interface
solves them.

In the first case, dev_close(conduit) triggers the NETDEV_GOING_DOWN
event in dsa_user_netdevice_event() which closes user ports as well.
dsa_port_disable_rt() calls phylink_stop(), which synchronously stops
the phylink state machine, and ds->ops->phy_read() will thus no longer
call into the driver after this point.

In the second case, dev_close(conduit) should do this, as per
Documentation/networking/driver.rst:

| Quiescence
| ----------
|
| After the ndo_stop routine has been called, the hardware must
| not receive or transmit any data.  All in flight packets must
| be aborted. If necessary, poll or wait for completion of
| any reset commands.

So it should be sufficient to ensure that later, when we zeroize
conduit->dsa_ptr, there will be no concurrent dsa_switch_rcv() call
on this conduit.

The addition of the netif_device_detach() function is to ensure that
ioctls, rtnetlinks and ethtool requests on the user ports no longer
propagate down to the driver - we're no longer prepared to handle them.

The race condition actually did not exist when commit 0650bf52b31f
("net: dsa: be compatible with masters which unregister on shutdown")
first introduced dsa_switch_shutdown(). It was created later, when we
stopped unregistering the user interfaces from a bad spot, and we just
replaced that sequence with a racy zeroization of conduit->dsa_ptr
(one which doesn't ensure that the interfaces aren't up).

Weakness: CWE-476 (NULL Pointer Dereference), CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2024-49998?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-49998?

Apply the vendor's patch.

## Is CVE-2024-49998 being exploited?

There is no known exploitation of CVE-2024-49998 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-49998 and fix it if it is affected.

What it is: CVE-2024-49998 is a medium-severity vulnerability in Linux kernel, published on 21 Oct 2024. 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-2024-49998 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2024-49998/ (Markdown: https://insights.sbomify.com/CVE-2024-49998/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-49998
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-49998
- OSV: https://osv.dev/vulnerability/CVE-2024-49998

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-49998/
Summaries are generated and may contain mistakes; the official description above is the record.