CVE-2026-44483

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+:

{
  "dependencies": { "@rvf/core": "8.1.0" },
  "overrides": { "@rvf/set-get": "7.0.1" }
}

const { preprocessFormData } = require('@rvf/core');

const form = new FormData();
form.append("username", "alice");
form.append("__proto__[polluted]", "yes");

preprocessFormData(form);
console.log(({}).polluted); // -> 'yes'

The field name __proto__[polluted] is the kind of value an attacker can submit from any HTML form or HTTP client. After the call, every plain object in the process inherits polluted = 'yes'.

A second working payload is constructor.prototype.<key>=<value>, which goes through setPath walking constructor then prototype.

CVSS

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L (8.2, High)

Integrity is High because the primitive lets the attacker change the meaning of property reads on every object in the process. Confidentiality is None and Availability is Low without a named downstream gadget; both could be higher in a specific consuming app.

Remediation for users

Upgrade to @rvf/set-get 7.0.2 or 6.0.4. If you cannot upgrade @rvf/core directly, an npm / pnpm override on @rvf/set-get works.

Credit

Reported by Mohamed Bassia (@0xBassia).

• Any property assignable on Object.prototype of the server process, set by a single unauthenticated HTTP request.
• Persists for the life of the worker process and affects every subsequent request handled by the same process.
• Direct downstream consequences depend on the host application and the rest of its dependency tree, but typical risks include: bypassing if (obj.isAdmin) style checks, injecting unintended config values into objects merged with user input, breaking template rendering, and crashing the worker by polluting properties used by other libraries (DoS).
• Worth noting: the visible output of preprocessFormData does not contain the malicious key, so the attack leaves no obvious trace in request logs that show parsed bodies.

CVE-2026-44483 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (7.0.2, 6.0.4); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44483? CVE-2026-44483 is a high-severity security vulnerability in @rvf/set-get (npm), affecting versions >= 7.0.0, < 7.0.2. It is fixed in 7.0.2, 6.0.4.
2. How severe is CVE-2026-44483? CVE-2026-44483 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @rvf/set-get are affected by CVE-2026-44483? @rvf/set-get (npm) versions >= 7.0.0, < 7.0.2 is affected.
4. Is there a fix for CVE-2026-44483? Yes. CVE-2026-44483 is fixed in 7.0.2, 6.0.4. Upgrade to this version or later.
5. Is CVE-2026-44483 exploitable, and should I be worried? Whether CVE-2026-44483 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44483 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44483?
   • Upgrade @rvf/set-get to 7.0.2 or later
   • Upgrade @rvf/set-get to 6.0.4 or later