# CVE-2025-38566: sunrpc: fix handling of server side tls alerts

> A flaw in Linux kernel NFS over TLS handling allows attackers to cause a denial of service by triggering improper TLS alert processing.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 19 Aug 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-66485, BELL-CVE-2025-38566, DEBIAN-CVE-2025-38566, GHSA-64hp-5254-q6pc, ROOT-OS-DEBIAN-13-CVE-2025-38566, ROOT-OS-UBUNTU-2404-CVE-2025-38566, UBUNTU-CVE-2025-38566

## What is CVE-2025-38566?

CVE-2025-38566 is a critical denial of service vulnerability in Linux kernel, published on 19 Aug 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:

sunrpc: fix handling of server side tls alerts

Scott Mayhew discovered a security exploit in NFS over TLS in
tls_alert_recv() due to its assumption it can read data from
the msg iterator's kvec..

kTLS implementation splits TLS non-data record payload between
the control message buffer (which includes the type such as TLS
aler or TLS cipher change) and the rest of the payload (say TLS
alert's level/description) which goes into the msg payload buffer.

This patch proposes to rework how control messages are setup and
used by sock_recvmsg().

If no control message structure is setup, kTLS layer will read and
process TLS data record types. As soon as it encounters a TLS control
message, it would return an error. At that point, NFS can setup a
kvec backed msg buffer and read in the control message such as a
TLS alert. Msg iterator can advance the kvec pointer as a part of
the copy process thus we need to revert the iterator before calling
into the tls_alert_recv.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2025-38566?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-38566?

Apply the vendor's patch.

## Is CVE-2025-38566 being exploited?

There is no known exploitation of CVE-2025-38566 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-2025-38566 and fix it if it is affected.

What it is: CVE-2025-38566 is a critical denial of service vulnerability in Linux kernel, published on 19 Aug 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-2025-38566 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-2025-38566/ (Markdown: https://insights.sbomify.com/CVE-2025-38566/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38566
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38566
- OSV: https://osv.dev/vulnerability/CVE-2025-38566

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38566/
Summaries are generated and may contain mistakes; the official description above is the record.