Bug 2544817 (CVE-2026-104183)

Summary: CVE-2026-104183 stream-json: stream-json: Object prototype manipulation via crafted JSON input
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: cdrage, rushinde
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in stream-json. When parsing JSON data, the Assembler component directly assigns properties, allowing an input key named '__proto__' to replace a parsed object's internal prototype rather than creating a standard property. An attacker who supplies crafted input can exploit this behavior to inject unexpected properties into parsed objects, potentially causing incorrect application decisions or service disruption.
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Description OSIDB Bzimport 2026-10-01 23:05:04 UTC 
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.