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Remote Code Execution in scratch-vm

Critical severity GitHub Reviewed Published Jul 27, 2020 to the GitHub Advisory Database • Updated Sep 12, 2023

Package

npm scratch-vm (npm)

Affected versions

<= 0.2.0-prerelease.20200709173451

Patched versions

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.

References

Reviewed Jul 27, 2020
Published to the GitHub Advisory Database Jul 27, 2020
Last updated Sep 12, 2023

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

0.501%
(76th percentile)

Weaknesses

CVE ID

CVE-2020-14000

GHSA ID

GHSA-vc9j-fhvv-8vrf

Source code

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