CVE-2020-14000: Mit Scratch-Vm

Critical severity, CVSS 9.8. EPSS: 2.8% chance of exploitation in the next 30 days.

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.

Affected products

• Mit Scratch-Vm: before 0.2.0-prerelease.20200714185213 (fixed in 0.2.0-prerelease.20200714185213)

Published 2020-07-16. Last modified 2026-06-17.