CVE-2026-104183stream-json: Prototype pollution: Assembler writes this.current[this.key] on plain objects
- 5.1MediumCVSS base score
- 0.19%Exploitation in 30 daysEPSS · top 91% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- YesPublic exploitsa reference or SSVC says so
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.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. A reference of the record is tagged as an exploit. CISA's SSVC rates its exploitation: a proof of concept is public.
Show the exploits1
References tagged exploit1 reference
- https://github.com/uhop/stream-json/security/advisories/GHSA-mjw6-4jj6-33hc (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium5.1 | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |
| NVDNVD · Deferred | 3.1 | Medium5.1 | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |
- EPSS (exploitation in 30 days)
- 0.19% · top 91% of all CVEs (12 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.1.
Affected products
- affected < 3.6.0
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- npmstream-jsonGHSA-mjw6-4jj6-33hc (opens in a new tab)
References
References3
- https://github.com/uhop/stream-json/security/advisories/GHSA-mjw6-4jj6-33hc (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/uhop/stream-json/commit/2f2d35bbb547306991ded6487a279154d865a358 (opens in a new tab)x_refsource_MISC
- https://github.com/uhop/stream-json/releases/tag/3.6.0 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-91057 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-mjw6-4jj6-33hc (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-104183)Record last updated .