# CVE-2021-3592: Information disclosure in QEMU

> A malicious guest can leak 10 bytes of uninitialized heap memory from the host via a crafted UDP packet in QEMU's SLiRP implementation.

- **Severity:** Low 3.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Jun 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-3592, GHSA-xrpp-vwp4-q9hp, UBUNTU-CVE-2021-3592

## What is CVE-2021-3592?

CVE-2021-3592 is a low-severity vulnerability in Debian Debian Linux, published on 15 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An invalid pointer initialization issue was found in the SLiRP networking implementation of QEMU. The flaw exists in the bootp_input() function and could occur while processing a udp packet that is smaller than the size of the 'bootp_t' structure. A malicious guest could use this flaw to leak 10 bytes of uninitialized heap memory from the host. The highest threat from this vulnerability is to data confidentiality. This flaw affects libslirp versions prior to 4.6.0.

Weakness: CWE-824 (Access of Uninitialized Pointer)

## Which versions are affected by CVE-2021-3592?

It affects 4 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Libslirp Project Libslirp, Redhat Enterprise Linux.

## How do I fix CVE-2021-3592?

Upgrade to a fixed version.

## Is CVE-2021-3592 being exploited?

There is no known exploitation of CVE-2021-3592 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3592 and fix it if it is affected.

What it is: CVE-2021-3592 is a low-severity vulnerability in Debian Debian Linux, published on 15 Jun 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-2021-3592 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-3592/ (Markdown: https://insights.sbomify.com/CVE-2021-3592/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3592
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3592
- OSV: https://osv.dev/vulnerability/CVE-2021-3592

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3592/
Summaries are generated and may contain mistakes; the official description above is the record.