Remote Code Execution in scratch-vm

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2020-14000: 2.83% estimated exploitation activity in the next 30 days; percentile 86.64 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

27 Jul 2020, 19:55 UTC

Last modified by the source

8 Nov 2023, 04:02 UTC

Source last checked

26 Oct 2026, 12:26 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vc9j-fhvv-8vrf

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-vc9j-fhvv-8vrf

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# Patch Next advisory brief: CVE-2020-14000

Advisory: Remote Code Execution in scratch-vm
IDs: CVE-2020-14000, GHSA-vc9j-fhvv-8vrf
Record: https://patchnext.com/advisories/cve-2020-14000 (revision 2, source checked 26 Oct 2026, 12:26 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: scratch-vm 0.2.0-prerelease.20200714185213. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm scratch-vm: affected <= 0.2.0-prerelease.20200709173451; fixed in 0.2.0-prerelease.20200714185213

## Suggested inspection (read-only)
- `npm ls scratch-vm --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on scratch-vm.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-vc9j-fhvv-8vrf (OSV record GHSA-vc9j-fhvv-8vrf lists affected ranges: npm scratch-vm >=0 <0.2.0-prerelease.20200714185213 (fixed))
- Verified: https://github.com/advisories/GHSA-vc9j-fhvv-8vrf (GitHub-reviewed advisory GHSA-vc9j-fhvv-8vrf lists affected ranges: npm scratch-vm >=0 <=0.2.0-prerelease.20200709173451)

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