# CVE-2020-35506: Use after free in QEMU

> A privileged guest user can trigger a use-after-free in QEMU's am53c974 emulation, causing host denial of service or code execution.

- **Severity:** Medium 6.7 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 May 2021
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-35506, GHSA-qfjc-pj3q-qmpf

## What is CVE-2020-35506?

CVE-2020-35506 is a medium-severity use after free vulnerability in Qemu Qemu, published on 28 May 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A use-after-free vulnerability was found in the am53c974 SCSI host bus adapter emulation of QEMU in versions before 6.0.0 during the handling of the 'Information Transfer' command (CMD_TI). This flaw allows a privileged guest user to crash the QEMU process on the host, resulting in a denial of service or potential code execution with the privileges of the QEMU process.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2020-35506?

It affects 1 product.


Products: Qemu Qemu.

## How do I fix CVE-2020-35506?

Upgrade to a fixed version.

## Is CVE-2020-35506 being exploited?

There is no known exploitation of CVE-2020-35506 in the wild and no public exploit code.

## Other vulnerabilities in Qemu Qemu

- [CVE-2022-36648](https://insights.sbomify.com/CVE-2022-36648/): Null dereference in n/a (critical 10.0)
- [CVE-2015-8556](https://insights.sbomify.com/CVE-2015-8556/): Race condition in n/a (critical 10.0)
- [CVE-2009-3616](https://insights.sbomify.com/CVE-2009-3616/): Use after free in n/a (critical 9.9)
- [CVE-2019-12928](https://insights.sbomify.com/CVE-2019-12928/): Command injection in n/a (critical 9.8)
- [CVE-2019-12929](https://insights.sbomify.com/CVE-2019-12929/): Command injection in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-35506 and fix it if it is affected.

What it is: CVE-2020-35506 is a medium-severity use after free vulnerability in Qemu Qemu, published on 28 May 2021. 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-2020-35506 in the wild and no public exploit code.

Affected product: Qemu Qemu. 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-2020-35506/ (Markdown: https://insights.sbomify.com/CVE-2020-35506/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-35506
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-35506
- OSV: https://osv.dev/vulnerability/CVE-2020-35506

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-35506/
Summaries are generated and may contain mistakes; the official description above is the record.