Prototype Pollution in parse-nested-form-data via `__proto__` in FormData field names
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · Low
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| milamer | parse-nested-form-data | before 1.0.1 | 1.0.1 | Patch available | CNA |
| — | parse-nested-form-data (npm) | before 1.0.1 | 1.0.1 | Patch available | GHSA-xp7r-j8r6-j9h3 |
- parse-nested-form-data Vendormilamer Affected before 1.0.1 Fixed in 1.0.1 Patch available CNA
- parse-nested-form-data (npm) Vendor— Affected before 1.0.1 Fixed in 1.0.1 Patch available GHSA-xp7r-j8r6-j9h3
Remediation
- Fix · CNA parse-nested-form-data (milamer) Fixed in 1.0.1
- Fix · GHSA-xp7r-j8r6-j9h3 parse-nested-form-data (npm) Fixed in 1.0.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-45302
- 2026-10-03 Alias added: GHSA-xp7r-j8r6-j9h3
References
Other 4
- https://github.com/milamer/parse-nested-form-data/security/advisories/GHSA-xp7r-j8r6-j9h3
- https://github.com/milamer/parse-nested-form-data/commit/527ad58eb486e32438f7198fb88315c20449d792
- https://github.com/milamer/parse-nested-form-data/releases/tag/v1.0.1
- https://github.com/milamer/parse-nested-form-data
Sources
- CVE-2026-45302 · CVE Program
- CVE-2026-45302 · NVD
- FIRST EPSS
- GHSA-xp7r-j8r6-j9h3 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences