# CVE-2021-47511: ALSA: pcm: oss: Fix negative period/buffer sizes

> A local attacker can trigger a denial of service in the Linux kernel by exploiting an integer overflow in the ALSA OSS layer's period size calculation.

- **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:** 24 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47511, UBUNTU-CVE-2021-47511

## What is CVE-2021-47511?

CVE-2021-47511 is a medium-severity vulnerability in Linux kernel, published on 24 May 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:

ALSA: pcm: oss: Fix negative period/buffer sizes

The period size calculation in OSS layer may receive a negative value
as an error, but the code there assumes only the positive values and
handle them with size_t.  Due to that, a too big value may be passed
to the lower layers.

This patch changes the code to handle with ssize_t and adds the proper
error checks appropriately.

## Which versions are affected by CVE-2021-47511?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47511?

Apply the vendor's patch.

## Is CVE-2021-47511 being exploited?

There is no known exploitation of CVE-2021-47511 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-2021-47511 and fix it if it is affected.

What it is: CVE-2021-47511 is a medium-severity vulnerability in Linux kernel, published on 24 May 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-2021-47511 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-2021-47511/ (Markdown: https://insights.sbomify.com/CVE-2021-47511/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47511
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47511
- OSV: https://osv.dev/vulnerability/CVE-2021-47511

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47511/
Summaries are generated and may contain mistakes; the official description above is the record.