---
id: CVE-2026-104183
title: >-
  stream-json is a micro-library of stream components for processing JSON and
  JSONC with a minimal memory footprint
summary: >-
  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 th…
severity: medium
cvss: 5.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L'
cwe:
  - CWE-1321
vendor: uhop
product: stream-json
affected:
  - stream-json < 3.6.0
published: '2026-10-01'
updated: '2026-10-01'
sourceUpdated: '2026-10-01T21:17:19.197'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-104183'
references:
  - url: >-
      https://github.com/uhop/stream-json/commit/2f2d35bbb547306991ded6487a279154d865a358
    label: security-advisories@github.com
  - url: 'https://github.com/uhop/stream-json/releases/tag/3.6.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/uhop/stream-json/security/advisories/GHSA-mjw6-4jj6-33hc
    label: security-advisories@github.com
  - url: >-
      https://github.com/uhop/stream-json/security/advisories/GHSA-mjw6-4jj6-33hc
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-01T20:29:33.204136Z'
ingestedAt: '2026-10-01T21:00:32.270Z'
---

## Overview

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

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.