NextAuth.js is a complete open source authentication solution for Next.js applications. In affected versions an attacker can send a request to an app using NextAuth.js with an invalid `callbackUrl` query parameter, which internally is converted to a `URL` object. The URL instantiation would fail due to a malformed URL being passed into the constructor, causing it to throw an unhandled error which led to the **API route handler timing out and logging in to fail**. This has been remedied in versions 3.29.5 and 4.5.0. If for some reason you cannot upgrade, the workaround requires you to rely on Advanced Initialization. Please see the documentation for more.

Affected: npm: next-auth

### Impact

An attacker can send a request to an app using NextAuth.js with an invalid `callbackUrl` query parameter, which internally we convert to a `URL` object. The URL instantiation would fail due to a malformed URL being passed into the constructor, causing it to throw an unhandled error which led to our **API route handler timing out and logging in to fail**. This has been remedied in the following releases:

next-auth v3 users before version 3.29.5 are impacted. (We recommend upgrading to v4, as v3 is considered unmaintained. See our [migration guide](https://next-auth.js.org/getting-started/upgrade-v4))

next-auth v4 users before version 4.5.0 are impacted.

### Patches

We've released patches for this vulnerability in: - v3 - `3.29.5` - v4 - `4.5.0`

You can do:

```sh npm i next-auth@latest ```

or

```sh yarn add next-auth@latest ```

or

```sh pnpm add next-auth@latest ```

(This will update to the latest v4 version, but you can change `latest` to `3` if you want to stay on v3. This is not recommended.)

### Workarounds

If for some reason you cannot upgrade, the workaround requires you to rely on [Advanced Initialization](https://next-auth.js.org/configuration/initialization#advanced-initialization). Here is an example:

**Before:**

```js // pages/api/auth/[...nextauth].js import NextAuth from "next-auth"

export default NextAuth(/* your config */) ```

**After:**

```js // pages/api/auth/[...nextauth].js import NextAuth from "next-auth"

function isValidH…