# CVE-2025-40347: net: enetc: fix the deadlock of enetc_mdio_lock

> A deadlock in the enetc network driver causes system hangs on RT kernels, requiring a kernel patch to resolve.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40347, DEBIAN-CVE-2025-40347, GHSA-r9fm-4g8c-9hfh, ROOT-OS-DEBIAN-11-CVE-2025-40347, ROOT-OS-DEBIAN-12-CVE-2025-40347, ROOT-OS-UBUNTU-2204-CVE-2025-40347, ROOT-OS-UBUNTU-2404-CVE-2025-40347, UBUNTU-CVE-2025-40347

## What is CVE-2025-40347?

CVE-2025-40347 is a high-severity vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

net: enetc: fix the deadlock of enetc_mdio_lock

After applying the workaround for err050089, the LS1028A platform
experiences RCU stalls on RT kernel. This issue is caused by the
recursive acquisition of the read lock enetc_mdio_lock. Here list some
of the call stacks identified under the enetc_poll path that may lead to
a deadlock:

enetc_poll
  -> enetc_lock_mdio
  -> enetc_clean_rx_ring OR napi_complete_done
     -> napi_gro_receive
        -> enetc_start_xmit
           -> enetc_lock_mdio
           -> enetc_map_tx_buffs
           -> enetc_unlock_mdio
  -> enetc_unlock_mdio

After enetc_poll acquires the read lock, a higher-priority writer attempts
to acquire the lock, causing preemption. The writer detects that a
read lock is already held and is scheduled out. However, readers under
enetc_poll cannot acquire the read lock again because a writer is already
waiting, leading to a thread hang.

Currently, the deadlock is avoided by adjusting enetc_lock_mdio to prevent
recursive lock acquisition.

## Which versions are affected by CVE-2025-40347?


## How do I fix CVE-2025-40347?

Apply the vendor's patch.

## Is CVE-2025-40347 being exploited?

There is no known exploitation of CVE-2025-40347 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40347 and fix it if it is affected.

What it is: CVE-2025-40347 is a high-severity vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40347 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-2025-40347/ (Markdown: https://insights.sbomify.com/CVE-2025-40347/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40347
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40347
- OSV: https://osv.dev/vulnerability/CVE-2025-40347

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40347/
Summaries are generated and may contain mistakes; the official description above is the record.