CVE-2022-35924

NextAuth.js is a complete open source authentication solution for Next.js applications. next-auth users who are using the EmailProvider either in versions before 4.10.3 or 3.29.10 are affected. If an attacker could forge a request that sent a comma-separated list of emails (eg.: attacker@attacker.com,victim@victim.com) to the sign-in endpoint, NextAuth.js would send emails to both the attacker and the victims e-mail addresses. The attacker could then login as a newly created user with the email being attacker@attacker.com,victim@victim.com. This means that basic authorization like email.endsWith(@victim.com) in the signIn callback would fail to communicate a threat to the developer and would let the attacker bypass authorization, even with an @attacker.com address. This vulnerability has been patched in v4.10.3 and v3.29.10 by normalizing the email value that is sent to the sign-in endpoint before accessing it anywhere else. We also added a normalizeIdentifier callback on the EmailProvider configuration, where you can further tweak your requirements for what your system considers a valid e-mail address. (E.g.: strict RFC2821 compliance). Users are advised to upgrade. There are no known workarounds for this vulnerability. If for some reason you cannot upgrade, you can normalize the incoming request using Advanced Initialization.

Weakness

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

Affected Software

Extended Description

Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user’s privileges and any permissions or other access-control specifications that apply to the resource. When access control checks are incorrectly applied, users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.

Potential Mitigations

• Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
• Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
• For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
• One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

References

• https://en.wikipedia.org/wiki/Email_address#Local-part
• https://github.com/nextauthjs/next-auth/commit/afb1fcdae3cc30445038ef588e491d139b916003
• https://github.com/nextauthjs/next-auth/security/advisories/GHSA-xv97-c62v-4587
• https://next-auth.js.org/configuration/callbacks#sign-in-callback
• https://next-auth.js.org/configuration/initialization#advanced-initialization
• https://next-auth.js.org/providers/email
• https://next-auth.js.org/providers/email#normalizing-the-e-mail-address
• https://nodemailer.com/message/addresses