# CVE-2020-1983: libslirp: use after free vulnerability cause a denial of service.

> Crafted packets trigger a use-after-free in libslirp, causing a denial of service for applications using this network library.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Apr 2020
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2020-1983, GHSA-m3gw-pxj4-v7p8, SUSE-SU-2020:1197-1, SUSE-SU-2020:1502-1, SUSE-SU-2020:1516-1, UBUNTU-CVE-2020-1983, openSUSE-SU-2020:0636-1, openSUSE-SU-2020:0756-1

## What is CVE-2020-1983?

CVE-2020-1983 is a high-severity use after free vulnerability in Canonical Ubuntu Linux, published on 22 Apr 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A use after free vulnerability in ip_reass() in ip_input.c of libslirp 4.2.0 and prior releases allows crafted packets to cause a denial of service.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2020-1983?

It affects 5 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `qemu` | SUSE:Linux Enterprise Module for Basesystem 15 SP1 | All versions | 3.1.1.1-9.21.4 |
| `slirp4netns` | SUSE:Linux Enterprise Module for Containers 15 SP1 | All versions | 0.4.5-3.9.1 |
| `qemu` | SUSE:Linux Enterprise Module for Server Applications 15 SP1 | All versions | 3.1.1.1-9.21.4 |
| `qemu` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 3.1.1.1-3.14.1 |
| `qemu` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 3.1.1.1-3.14.1 |
| `qemu` | openSUSE:Leap 15.1 | All versions | 3.1.1.1-lp151.7.15.2 |
| `qemu-linux-user` | openSUSE:Leap 15.1 | All versions | 3.1.1.1-lp151.7.15.2 |
| `slirp4netns` | openSUSE:Leap 15.1 | All versions | 0.4.5-lp151.2.9.1 |

Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Libslirp Project Libslirp, Opensuse Leap.

## How do I fix CVE-2020-1983?

Upgrade to a fixed version.

## Is CVE-2020-1983 being exploited?

There is no known exploitation of CVE-2020-1983 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-1983 and fix it if it is affected.

What it is: CVE-2020-1983 is a high-severity use after free vulnerability in Canonical Ubuntu Linux, published on 22 Apr 2020. 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-2020-1983 in the wild and no public exploit code.

Affected product: Canonical Ubuntu 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-2020-1983/ (Markdown: https://insights.sbomify.com/CVE-2020-1983/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1983
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1983
- OSV: https://osv.dev/vulnerability/CVE-2020-1983

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1983/
Summaries are generated and may contain mistakes; the official description above is the record.