CVE-2026-40155: Auth0 Next.js SDK has Improper Proxy Cache Lookup
Description In affected versions of the Next.js SDK, simultaneous requests that trigger a nonce retry may cause the proxy cache fetcher to perform improper lookups for the token request results.
Which Projects are Affected? Users are affected if they meet all of the following preconditions: - Applications using the auth0/nextjs-auth0 SDK, versions 4.12.0 to 4.17.0, and - Applications using the proxy handler /me/ and /my-org/ with DPoP enabled.
Affected product and versions Auth0/nextjs-auth0 v4.12.0 to 4.17.0
Resolution Upgrade Auth0/nextjs-auth0 version to v4.18.0 or greater
Acknowledgements Okta would like to thank Reynaldo Immanuel for their discovery and responsible disclosure.
Other sources
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.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-40155?
The severity of CVE-2026-40155 is rated as moderate due to the potential for improper proxy cache lookups affecting user authentication.
How do I fix CVE-2026-40155?
To fix CVE-2026-40155, update the Auth0 Next.js SDK to version 4.18.0 or later.
Who is affected by CVE-2026-40155?
CVE-2026-40155 affects users of the Auth0 Next.js SDK versions 4.12.0 through 4.17.1.
What are the consequences of CVE-2026-40155?
The consequences of CVE-2026-40155 include potential unauthorized access due to improper handling of proxy cache lookups.
When was CVE-2026-40155 published?
CVE-2026-40155 was published in 2026, highlighting vulnerabilities in specific versions of the Auth0 Next.js SDK.