{"id":"CVE-2020-14000","aliases":["EUVD-2020-0570","GHSA-vc9j-fhvv-8vrf"],"status":"published","title":"Remote Code Execution in scratch-vm","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.","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-11","score":0.0283,"percentile":0.86798,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-502"],"published":"2020-07-16T14:41:40Z","modified":"2026-06-17T02:54:04Z","fixes":[{"ecosystem":"npm","package":"scratch-vm","fixed_in":["0.2.0-prerelease.20200714185213"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"scratch-vm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"0.2.0-prerelease.20200709173451"},{"fixed":"0.2.0-prerelease.20200714185213"}]}]},{"source":"osv","ecosystem":"npm","package":"scratch-vm","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.2.0-prerelease.20200714185213"}]}]}],"products":[{"vendor":"mit","product":"scratch-vm"}],"references":[{"url":"https://github.com/LLK/scratch-vm/pull/2476","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","web"]},{"url":"https://scratch.mit.edu/discuss/topic/422904/?page=1#post-4223443","tags":["x_refsource_CONFIRM","x_transferred","Vendor Advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-14000","tags":["advisory"]},{"url":"https://github.com/LLK/scratch-vm/pull/2476/commits/90b9da45f4084958535338d1c4d71a22d6136aab","tags":["web"]},{"url":"https://github.com/advisories/GHSA-vc9j-fhvv-8vrf"},{"url":"https://github.com/LLK/scratch-vm","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2020-14000","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.","status":"published","published":"2020-07-16T14:41:40Z","modified":"2024-08-04T12:32:14.707Z","updated_at":"2026-11-02T14:35:46.873079Z"}],"euvd":[{"id":"EUVD-2020-0570","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.","status":"published","published":"2020-07-16T14:41:40Z","modified":"2024-08-04T12:32:14Z","updated_at":"2026-11-03T03:07:36.182524Z"}],"ghsa":[{"id":"GHSA-vc9j-fhvv-8vrf","title":"Remote Code Execution in scratch-vm","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. \n\n**NOTE**: the scratch.mit.edu hosted service is not affected because of the lack of worker scripts.","status":"published","published":"2020-07-27T19:55:52Z","modified":"2023-09-12T18:20:35Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-502"],"updated_at":"2026-11-02T14:37:04.447845Z"}],"nvd":[{"id":"CVE-2020-14000","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.","status":"published","published":"2020-07-16T15:15:27.86Z","modified":"2026-06-17T02:54:04.837Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"cwes":["CWE-502"],"updated_at":"2026-11-02T14:06:10.086163Z"}],"osv":[{"id":"GHSA-vc9j-fhvv-8vrf","title":"Remote Code Execution in scratch-vm","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. \n\n**NOTE**: the scratch.mit.edu hosted service is not affected because of the lack of worker scripts.","status":"published","published":"2020-07-27T19:55:52Z","modified":"2023-11-08T04:02:24.878433Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-502"],"updated_at":"2026-11-02T15:46:56.981655Z"}]}}