# CVE-2025-21701: net: avoid race between device unregistration and ethnl ops

> A race condition in the Linux kernel network subsystem can cause a system crash when modifying network device channels during unregistration.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 13 Feb 2025
- **Updated:** 15 Oct 2026
- **Also known as:** A-392852041, ASB-A-392852041, BELL-CVE-2025-21701, DEBIAN-CVE-2025-21701, GHSA-268v-p5rc-rhmv, ROOT-OS-DEBIAN-11-CVE-2025-21701, UBUNTU-CVE-2025-21701

## What is CVE-2025-21701?

CVE-2025-21701 is a high-severity vulnerability in Linux kernel, published on 13 Feb 2025. 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: avoid race between device unregistration and ethnl ops

The following trace can be seen if a device is being unregistered while
its number of channels are being modified.

  DEBUG_LOCKS_WARN_ON(lock->magic != lock)
  WARNING: CPU: 3 PID: 3754 at kernel/locking/mutex.c:564 __mutex_lock+0xc8a/0x1120
  CPU: 3 UID: 0 PID: 3754 Comm: ethtool Not tainted 6.13.0-rc6+ #771
  RIP: 0010:__mutex_lock+0xc8a/0x1120
  Call Trace:
   <TASK>
   ethtool_check_max_channel+0x1ea/0x880
   ethnl_set_channels+0x3c3/0xb10
   ethnl_default_set_doit+0x306/0x650
   genl_family_rcv_msg_doit+0x1e3/0x2c0
   genl_rcv_msg+0x432/0x6f0
   netlink_rcv_skb+0x13d/0x3b0
   genl_rcv+0x28/0x40
   netlink_unicast+0x42e/0x720
   netlink_sendmsg+0x765/0xc20
   __sys_sendto+0x3ac/0x420
   __x64_sys_sendto+0xe0/0x1c0
   do_syscall_64+0x95/0x180
   entry_SYSCALL_64_after_hwframe+0x76/0x7e

This is because unregister_netdevice_many_notify might run before the
rtnl lock section of ethnl operations, eg. set_channels in the above
example. In this example the rss lock would be destroyed by the device
unregistration path before being used again, but in general running
ethnl operations while dismantle has started is not a good idea.

Fix this by denying any operation on devices being unregistered. A check
was already there in ethnl_ops_begin, but not wide enough.

Note that the same issue cannot be seen on the ioctl version
(__dev_ethtool) because the device reference is retrieved from within
the rtnl lock section there. Once dismantle started, the net device is
unlisted and no reference will be found.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2025-21701?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21701?

Apply the vendor's patch.

## Is CVE-2025-21701 being exploited?

There is no known exploitation of CVE-2025-21701 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-2025-21701 and fix it if it is affected.

What it is: CVE-2025-21701 is a high-severity vulnerability in Linux kernel, published on 13 Feb 2025. 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-2025-21701 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-2025-21701/ (Markdown: https://insights.sbomify.com/CVE-2025-21701/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21701
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21701
- OSV: https://osv.dev/vulnerability/CVE-2025-21701

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21701/
Summaries are generated and may contain mistakes; the official description above is the record.