@rvf/set-get has a prototype pollution issue that's reachable via @rvf/core preprocessFormData (HTTP form data)
Date: 2026-05
Affected: npm/@rvf/set-get, npm/@rvf/set-get
Attack vector: other
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2026-44483
CWE: CWE-1321
CVSS: 8.2 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L)

## Summary `setPath` in `@rvf/set-get` (used by `@rvf/core` to flatten incoming form data into a nested object) does not block the keys `__proto__`, `constructor`, or `prototype` when walking a path. Because field names in submitted form data are passed directly to `setPath` via `preprocessFormData` (and through `parseFormData` / `validate`), an attacker who can submit a form to a Remix / React Router app using the library can set arbitrary properties on `Object.prototype` of the running server process. This is a default-reachable prototype pollution primitive: no special configuration is required. Any endpoint that accepts a form via `parseFormData` or runs a validator created with `createValidator` is affected. ## Affected versions - `@rvf/set-get` `< 7.0.2` (7.x line) - `@rvf/set-get` `< 6.0.4` (6.x line) Reached through `@rvf/core` versions that depend on a vulnerable `@rvf/set-get` (current `8.1.0` resolves to `7.0.1` without the override). ## Patched - `@rvf/set-get` `7.0.2` - `@rvf/set-get` `6.0.4` The fix adds a `REJECT_KEYS` blocklist (`__proto__`, `constructor`, `prototype`) and throws when one is encountered while walking a path inside `setPath`. ## Proof of concept Install a vulnerable resolution and run on Node 18+: ```json { "dependencies": { "@rvf/core": "8.1.0" }, "overrides": { "@rvf/set-get": "7.0.1" } } ``` ```js const { preprocessFormData } = require('@rvf/core'); const form = new FormData(); form.append("username", "alice"); form.append("


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