# CVE-2021-47241: ethtool: strset: fix message length calculation

> A flaw in the Linux kernel ethtool module causes a warning and potential crash when calculating message lengths for specific string set requests.

- **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:** 21 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47241, GHSA-hh94-frj2-pf9r, UBUNTU-CVE-2021-47241

## What is CVE-2021-47241?

CVE-2021-47241 is a high-severity denial of service vulnerability in Linux kernel, published on 21 May 2024. 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:

ethtool: strset: fix message length calculation

Outer nest for ETHTOOL_A_STRSET_STRINGSETS is not accounted for.
This may result in ETHTOOL_MSG_STRSET_GET producing a warning like:

    calculated message payload length (684) not sufficient
    WARNING: CPU: 0 PID: 30967 at net/ethtool/netlink.c:369 ethnl_default_doit+0x87a/0xa20

and a splat.

As usually with such warnings three conditions must be met for the warning
to trigger:
 - there must be no skb size rounding up (e.g. reply_size of 684);
 - string set must be per-device (so that the header gets populated);
 - the device name must be at least 12 characters long.

all in all with current user space it looks like reading priv flags
is the only place this could potentially happen. Or with syzbot :)

Weakness: CWE-266 (Incorrect Privilege Assignment)

## Which versions are affected by CVE-2021-47241?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47241?

Apply the vendor's patch.

## Is CVE-2021-47241 being exploited?

There is no known exploitation of CVE-2021-47241 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-2021-47241 and fix it if it is affected.

What it is: CVE-2021-47241 is a high-severity denial of service vulnerability in Linux kernel, published on 21 May 2024. 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-2021-47241 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-2021-47241/ (Markdown: https://insights.sbomify.com/CVE-2021-47241/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47241
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47241
- OSV: https://osv.dev/vulnerability/CVE-2021-47241

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47241/
Summaries are generated and may contain mistakes; the official description above is the record.