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

> A vulnerability in the Linux kernel dt9812 driver allows attackers to read stack memory or cause denial of service due to improper DMA buffer allocation.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47477, GHSA-6vq2-rrj2-6jjh, UBUNTU-CVE-2021-47477

## What is CVE-2021-47477?

CVE-2021-47477 is a medium-severity vulnerability in Linux kernel, published on 22 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:

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.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-47477?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47477?

Apply the vendor's patch.

## Is CVE-2021-47477 being exploited?

There is no known exploitation of CVE-2021-47477 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-2021-47477 and fix it if it is affected.

What it is: CVE-2021-47477 is a medium-severity vulnerability in Linux kernel, published on 22 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-2021-47477 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-2021-47477/ (Markdown: https://insights.sbomify.com/CVE-2021-47477/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47477
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47477
- OSV: https://osv.dev/vulnerability/CVE-2021-47477

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47477/
Summaries are generated and may contain mistakes; the official description above is the record.