# CVE-2020-14000: Remote Code Execution in scratch-vm

> Attackers can achieve remote code execution by crafting malicious project files that exploit unsafe URL loading in the Scratch VM library.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 16 Jul 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-vc9j-fhvv-8vrf

## What is CVE-2020-14000?

CVE-2020-14000 is a critical unsafe deserialization vulnerability in n/a, published on 16 Jul 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

MIT Lifelong Kindergarten Scratch scratch-vm before 0.2.0-prerelease.20200714185213 loads extension URLs from untrusted project.json files with certain _ characters, resulting in remote code execution because the URL's content is treated as a script and is executed as a worker. The responsible code is getExtensionIdForOpcode in serialization/sb3.js. The use of _ is incompatible with a protection mechanism in older versions, in which URLs were split and consequently deserialization attacks were prevented. NOTE: the scratch.mit.edu hosted service is not affected because of the lack of worker scripts.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2020-14000?

2 open source packages ship an affected version, including scratch-vm. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `scratch-vm` | npm | All versions | 0.2.0-prerelease.20200714185213 |
| `scratch-vm` | npm | All versions | 0.2.0-prerelease.20200714185213 |

Products: Mit Scratch-Vm.

## How do I fix CVE-2020-14000?

Upgrade scratch-vm to 0.2.0-prerelease.20200714185213 or later.

## Is CVE-2020-14000 being exploited?

There is no known exploitation of CVE-2020-14000 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-14000 and fix it if it is affected.

What it is: CVE-2020-14000 is a critical unsafe deserialization vulnerability in n/a, published on 16 Jul 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-2020-14000 in the wild and no public exploit code.

Affected packages and fixed versions:
- scratch-vm (npm): affected all versions; fixed in 0.2.0-prerelease.20200714185213
- scratch-vm (npm): affected all versions; fixed in 0.2.0-prerelease.20200714185213

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-2020-14000/ (Markdown: https://insights.sbomify.com/CVE-2020-14000/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-14000
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-14000
- OSV: https://osv.dev/vulnerability/CVE-2020-14000

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-14000/
Summaries are generated and may contain mistakes; the official description above is the record.