# CVE-2021-32846: Moby HyperKit uninitialized memory use in virtio-sock pci_vtsock_proc_tx

> A guest VM can crash the host or potentially execute code via uninitialized memory use in HyperKit's virtio-sock implementation.

- **Severity:** High 7.7 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Feb 2023
- **Updated:** 10 Mar 2025
- **Also known as:** GHSA-8j79-g729-4vv7

## What is CVE-2021-32846?

CVE-2021-32846 is a high-severity memory corruption vulnerability in moby hyperkit, published on 17 Feb 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

HyperKit is a toolkit for embedding hypervisor capabilities in an application. In versions 0.20210107, function `pci_vtsock_proc_tx` in `virtio-sock` can lead to to uninitialized memory use. In this situation, there is a check for the return value to be less or equal to `VTSOCK_MAXSEGS`, but that check is not sufficient because the function can return `-1` if it finds an error it cannot recover from. Moreover, the negative return value will be used by `iovec_pull` in a while condition that can further lead to more corruption because the function is not designed to handle a negative `iov_len`. This issue may lead to a guest crashing the host causing a denial of service and, under certain circumstance, memory corruption. This issue is fixed in commit af5eba2360a7351c08dfd9767d9be863a50ebaba.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions), CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2021-32846?

It affects 1 product.


Products: Mobyproject Hyperkit.

## How do I fix CVE-2021-32846?

No fix has been published for CVE-2021-32846 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-32846 being exploited?

There is no known exploitation of CVE-2021-32846 in the wild and no public exploit code.

## Other vulnerabilities in moby hyperkit

- [CVE-2021-32845](https://insights.sbomify.com/CVE-2021-32845/): Moby HyperKit uninitialized memory use vtrnd pci_vtrnd_notify (high 7.7)
- [CVE-2021-32847](https://insights.sbomify.com/CVE-2021-32847/): Moby HyperKit uninitialized memory use in virtio-sock pci_vtsock_proc_tx (high 7.1)
- [CVE-2021-32843](https://insights.sbomify.com/CVE-2021-32843/): Null dereference in hyperkit (medium 6.2)
- [CVE-2021-32844](https://insights.sbomify.com/CVE-2021-32844/): Null dereference in hyperkit (medium 6.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-32846 and fix it if it is affected.

What it is: CVE-2021-32846 is a high-severity memory corruption vulnerability in moby hyperkit, published on 17 Feb 2023. 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-2021-32846 in the wild and no public exploit code.

Affected product: moby hyperkit. 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-2021-32846/ (Markdown: https://insights.sbomify.com/CVE-2021-32846/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32846
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32846
- OSV: https://osv.dev/vulnerability/CVE-2021-32846

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32846/
Summaries are generated and may contain mistakes; the official description above is the record.