CVE-2026-45302CWE-1321

Prototype Pollution in parse-nested-form-data via `__proto__` in FormData field names

High · published June 1, 2026

CVSS v3.1
8.2
EPSS
1%
Percentile
46.0
In the wild
Unconfirmed
What it is

parse-nested-form-data is a tiny node module for parsing FormData by name into objects and arrays. Prior to version 1.0.1, parseFormData() walks bracket and dot-notation FormData field names into nested objects without filtering reserved property keys. A single FormData field whose name begins with __proto__, or contains .__proto__. mid-path, causes the parser to traverse onto Object.prototype and assign properties there, polluting the prototype chain of every plain object in the running process. This issue has been patched in version 1.0.1.

The record
Technical detail
CVSS v3.1
8.2 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
CVSS v4.0
Not supplied
EPSS
0.00562 · 46.0th percentile
Weakness
CWE-1321 · Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Published
2026-06-01T17:20Z
EPSS history
Timeline
  • 01 JUN 17:20Z
    Prototype Pollution in parse-nested-form-data via `__proto__` in FormData field names
    cvelistv5