# CVE-2023-53606: nfsd: clean up potential nfsd_file refcount leaks in COPY codepath

> A refcount leak in the Linux kernel NFS server COPY codepath can lead to resource exhaustion and denial of service.

- **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:** 4 Oct 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2023-53606, DEBIAN-CVE-2023-53606, GHSA-vqjq-cm24-xjp3, UBUNTU-CVE-2023-53606

## What is CVE-2023-53606?

CVE-2023-53606 is a high-severity denial of service vulnerability in Linux kernel, published on 4 Oct 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:

nfsd: clean up potential nfsd_file refcount leaks in COPY codepath

There are two different flavors of the nfsd4_copy struct. One is
embedded in the compound and is used directly in synchronous copies. The
other is dynamically allocated, refcounted and tracked in the client
struture. For the embedded one, the cleanup just involves releasing any
nfsd_files held on its behalf. For the async one, the cleanup is a bit
more involved, and we need to dequeue it from lists, unhash it, etc.

There is at least one potential refcount leak in this code now. If the
kthread_create call fails, then both the src and dst nfsd_files in the
original nfsd4_copy object are leaked.

The cleanup in this codepath is also sort of weird. In the async copy
case, we'll have up to four nfsd_file references (src and dst for both
flavors of copy structure). They are both put at the end of
nfsd4_do_async_copy, even though the ones held on behalf of the embedded
one outlive that structure.

Change it so that we always clean up the nfsd_file refs held by the
embedded copy structure before nfsd4_copy returns. Rework
cleanup_async_copy to handle both inter and intra copies. Eliminate
nfsd4_cleanup_intra_ssc since it now becomes a no-op.

## Which versions are affected by CVE-2023-53606?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2023-53606?

Apply the vendor's patch.

## Is CVE-2023-53606 being exploited?

There is no known exploitation of CVE-2023-53606 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-2023-53606 and fix it if it is affected.

What it is: CVE-2023-53606 is a high-severity denial of service vulnerability in Linux kernel, published on 4 Oct 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-2023-53606 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-2023-53606/ (Markdown: https://insights.sbomify.com/CVE-2023-53606/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53606
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53606
- OSV: https://osv.dev/vulnerability/CVE-2023-53606

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53606/
Summaries are generated and may contain mistakes; the official description above is the record.