Skip to content
Fencer Vulns
medium 5.1

CVE-2026-104183 json

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

published 2026-10-01 38 d ago modified 2026-10-05 34 d ago also GHSA-mjw6-4jj6-33hc , EUVD-2026-91057

cvss
5.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

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 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.

Patch / fix

  • npm stream-json 3.6.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-104183 updated cvss 5.1

stream-json: stream-json: Object prototype manipulation via crafted JSON input

  • Red Hat Build of Podman Desktop rh-podman-desktop 3c6fc75a2a6cf5bb9b8a667fddcbbf428132badc
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
38 d ago

Exploit prediction

0.19% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/uhop/stream-json/security/advisories/GHSA-mjw6-4jj6-33hc referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
GitHub 3.1 5.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Affected packages

ecosystem package affected fixed in
npm stream-json
<3.6.0
3.6.0

Affected products

  • uhop stream-json

Classification

Weakness
  • CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.