auth0 nextjs-auth0 up to 4.17.x authorization

Summaryinfo

A vulnerability categorized as problematic has been discovered in auth0 nextjs-auth0 up to 4.17.x. Affected by this issue is some unknown functionality. The manipulation results in authorization. This vulnerability was named CVE-2026-40155. The attack may be performed from remote. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in auth0 nextjs-auth0 up to 4.17.x. Affected is an unknown functionality. The manipulation with an unknown input leads to a authorization vulnerability. CWE is classifying the issue as CWE-863. 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. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

The Auth0 Next.js SDK is a library for implementing user authentication in Next.js applications. In versions 4.12.0 through 4.17.1, simultaneous requests that trigger a nonce retry may cause the proxy cache fetcher to perform improper lookups for the token request results. Users are affected if their project uses both the vulnerable versions and the proxy handler /me/* and /my-org/* with DPoP enabled. This issue has been fixed in version 4.18.0.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-40155 since 04/09/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available.

Upgrading to version 4.18.0 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 98c36dc306970c2230ea1a32efef431d29b99978 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• auth0

Name

• nextjs-auth0

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17

License

• open-source

Website

• Product: https://github.com/auth0/nextjs-auth0/

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