Vulnerability · Published Jun 1, 2026 · Assigned by GitHub_M
CVE-2026-45302Prototype Pollution in parse-nested-form-data via `__proto__` in FormData field names
High 8.2
In plain English
A high-severity prototype pollution in parse-nested-form-data from milamer. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | parse-nested-form-data | 1.0.1 | GHSA-xp7r-j8r6-j9h3 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| milamer | parse-nested-form-data | < 1.0.1 |
Weakness: CWE-1321 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
References
- https://github.com/milamer/parse-nested-form-data/security/advisories/GHSA-xp7r-j8r6-j9h3 x_refsource_CONFIRM
- https://github.com/milamer/parse-nested-form-data/commit/527ad58eb486e32438f7198fb88315c20449d792 x_refsource_MISC
- https://github.com/milamer/parse-nested-form-data/releases/tag/v1.0.1 x_refsource_MISC