CVE-2020-14000: Deserialization of Untrusted Data

July 16, 2020 (updated July 24, 2020)

MIT Lifelong Kindergarten Scratch scratch-vm loads extension URLs from untrusted project.json files with certain _ characters, resulting in remote code execution because the URL 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.

References

nvd.nist.gov/vuln/detail/CVE-2020-14000
scratch.mit.edu/discuss/topic/422904/?page=1

Code Behaviors & Features

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