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GHSA-7r7x-4c4q-c4qf

HighCVSS 8.1 / 10

Published Mar 13, 2023·Last modified Nov 8, 2023

Affected Components(0)

No affected components available

Description

Impact

next-auth applications using OAuth provider versions before v4.20.1 are affected.

A bad actor who can spy on the victim's network or able to social engineer the victim to click a manipulated login link could intercept and tamper with the authorization URL to log in as the victim, bypassing the CSRF protection.

As an example, an attack can happen in the following scenario.

TL;DR: The attacker steals the victim's authenticated callback by intercepting and tampering with the authorization URL created by next-auth.

The victim attempts to log in to the next-auth site. For example https://next-auth-example.vercel.app/
next-auth sets the checks cookies according to how the OAuth provider is configured. In this case, state and pkce are set by default for the Google Provider.
<img width="1971" alt="Screen Shot 2023-03-03 at 09 54 26" src="https://user-images.githubusercontent.com/31528554/222619750-a2062bb8-99eb-4985-a75c-d75acd3da67e.png">
The attacker intercepts the returned authorization URL, strips away the OAuth check (nonce, state, pkce), and returns the URL without the check to the victim's browser. For example: From https://accounts.google.com/o/oauth2/v2/auth/oauthchooseaccount?client_id=client_id&scope=openid%20email%20profile&response_type=code&redirect_uri=https%3A%2F%2Fnext-auth-example.vercel.app%2Fapi%2Fauth%2Fcallback%2Fgoogle&state=state&code_challenge=code_challenge&code_challenge_method=S256&service=lso&o2v=2&flowName=GeneralOAuthFlow to https://accounts.google.com/o/oauth2/v2/auth/oauthchooseaccount?client_id=client_id&scope=openid%20email%20profile&response_type=code&redirect_uri=https%3A%2F%2Fnext-auth-example.vercel.app%2Fapi%2Fauth%2Fcallback%2Fgoogle&service=lso&o2v=2&flowName=GeneralOAuthFlow. Notice the parameters state, code_challenge and code_verifier are removed from the victim's address bar.
The victim attempts to log in using their OAuth account.
The Authorization Server logs the victim in and calls back to the next-auth api/auth/callback/:providerIdendpoint. 5.1. The attacker intercepts and logs this callback URL for later use. 5.2. next-auth checks the callback call from OAuth Authorization Server (doesn't have checks) and compares the checks with the cookies set (has checks) at step 2. This check will fail, resulting in the victim isn't logged in. However, at this step, the Authorization Server has already accepted the victim's request to log in and generated/sent a code in the URL.
The attacker now has an authorization URL with the code that the AS will exchange for valid access_token/id_token and can log in as the victim automatically. They can open a new browser window and paste in the URL logged at step 5.1 and log in as the victim.

Patches

We patched the vulnerability in next-auth v4.20.1 To upgrade, run one of the following:

npm i next-auth@latest

yarn add next-auth@latest

pnpm add next-auth@latest

Workarounds

Upgrading to latest is the recommended way to fix this issue. However, using Advanced Initialization, developers can manually check the callback request for state, pkce, and nonce against the provider configuration, and abort the sign-in process if there is a mismatch. Check out the source code for help.

References

Risk Scores

Base Score

8.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.

Threat Intelligence

7.4

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS

0.54%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit

Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity

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