# CVE-2021-46940: tools/power turbostat: Fix offset overflow issue in index converting

> An integer overflow in the Linux kernel turbostat tool prevents background stat updates, causing a denial of service for power monitoring.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 27 Feb 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-46940, GHSA-3whp-4394-49gc, UBUNTU-CVE-2021-46940

## What is CVE-2021-46940?

CVE-2021-46940 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 2024. 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:

tools/power turbostat: Fix offset overflow issue in index converting

The idx_to_offset() function returns type int (32-bit signed), but
MSR_PKG_ENERGY_STAT is u32 and would be interpreted as a negative number.
The end result is that it hits the if (offset < 0) check in update_msr_sum()
which prevents the timer callback from updating the stat in the background when
long durations are used. The similar issue exists in offset_to_idx() and
update_msr_sum(). Fix this issue by converting the 'int' to 'off_t' accordingly.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2021-46940?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-46940?

Apply the vendor's patch.

## Is CVE-2021-46940 being exploited?

There is no known exploitation of CVE-2021-46940 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-2021-46940 and fix it if it is affected.

What it is: CVE-2021-46940 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 2024. 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-2021-46940 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-2021-46940/ (Markdown: https://insights.sbomify.com/CVE-2021-46940/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-46940
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-46940
- OSV: https://osv.dev/vulnerability/CVE-2021-46940

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-46940/
Summaries are generated and may contain mistakes; the official description above is the record.