CVE-2026-104183

5.1 MEDIUM 0.2% exploit odds Fix listed Other Library

What it is

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.

At a glance

Exploitability: Can be exploited locally on the machine without logging in. Limited direct impact.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-10-01 21:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-02 18:47 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 5.1 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-10-01 21:17 UTC
Last modified: 2026-10-02 18:47 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-1321 · Prototype pollution
Record status: Deferred

Attack profile CVSS 3.1 · 5.1

Attack vector: Local
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: Low

Raw vector

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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-104183.md and follow it. Check whether this project is affected by CVE-2026-104183. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record