CVE-2026-104183

stream-json: Prototype pollution: Assembler writes this.current[this.key] on plain objects

Published Oct 1, 2026 CVSS 3.1 · 5.1 Medium EPSS < 1% KEV · Not listed
Description
stream-json is a micro-library of stream components for processing JSON and JSONC with a minimal memory footprint. Prior to 3.6.0, Assembler materializes object properties with plain assignment, so an input key named __proto__ invokes the inherited setter and causes parsed object prototype replacement instead of creating an own data property. Applications that make authorization or feature decisions from inherited values can therefore consume attacker-controlled properties, and a null prototype can disrupt code that expects Object.prototype methods. The researcher treats parsing untrusted JSON as part of the project contract, while the maintainer states that documented inputs are locally owned dumps, exports, or logs and characterizes the attack vector as local. The global Object.prototype is not polluted. This issue is fixed in version 3.6.0.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-mjw6-4jj6-33hc stream-json has a prototype pollution issue: Assembler writes this.current[this.key] on plain objects
History
Type Values Removed Values Added
First Time appeared Uhop
Uhop stream-json
Vendors & Products Uhop
Uhop stream-json
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description stream-json is a micro-library of stream components for processing JSON and JSONC with a minimal memory footprint. Prior to 3.6.0, Assembler materializes object properties with plain assignment, so an input key named __proto__ invokes the inherited setter and causes parsed object prototype replacement instead of creating an own data property. Applications that make authorization or feature decisions from inherited values can therefore consume attacker-controlled properties, and a null prototype can disrupt code that expects Object.prototype methods. The researcher treats parsing untrusted JSON as part of the project contract, while the maintainer states that documented inputs are locally owned dumps, exports, or logs and characterizes the attack vector as local. The global Object.prototype is not polluted. This issue is fixed in version 3.6.0.
Title stream-json: Prototype pollution: Assembler writes this.current[this.key] on plain objects
Weaknesses CWE-1321
References
Metrics cvssV3_1

{'score': 5.1, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 1, 2026, 8:30 PM
Reserved
Oct 1, 2026, 6:54 PM
Status
Deferred
Published
Oct 1, 2026, 9:17 PM
Modified
Oct 2, 2026, 6:47 PM
Severity
Moderate
Public date
Oct 1, 2026, 8:17 PM