Vulnerability · Published May 29, 2026 · Assigned by GitHub_M
CVE-2026-46510Prototype pollution in form-data-objectizer via bracket-notation form keys
High 8.2
In plain English
A high-severity prototype pollution in form-data-objectizer from kaspernj. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
form-data-objectizer converts FormData to object. Prior to 1.0.1, form-data-objectizer walks bracket-notation form keys (e.g. name[sub]) into nested objects without filtering __proto__, constructor, or prototype. A single HTTP form field whose name starts with __proto__[...] causes the library to mutate Object.prototype, which is a prototype pollution primitive of the entire Node.js process. This vulnerability is fixed in 1.0.1.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | form-data-objectizer | 1.0.1 | GHSA-m2hg-wjq3-28wq |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| kaspernj | form-data-objectizer | < 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