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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-104183
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-01 21:17:19 UTC
Updated2026-10-01 21:17:19 UTC
Descriptionstream-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.

Risk And Classification

Primary CVSS: v3.1 5.1 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Problem Types: CWE-1321 | CWE-1321 CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.1MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
3.1CNADECLARED5.1MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Uhop Stream-json affected < 3.6.0 Not specified

References

ReferenceSourceLinkTags
github.com/uhop/stream-json/releases/tag/3.6.0 [email protected] github.com
github.com/uhop/stream-json/security/advisories/GHSA-mjw6-4jj6-33hc 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/uhop/stream-json/commit/2f2d35bbb547306991ded6487a279154d865a358 [email protected] github.com
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