nextauthjs next-auth JWT /core/jwt getToken bearer input validation

Summaryinfo

A vulnerability categorized as problematic has been discovered in nextauthjs next-auth. This issue affects the function getToken of the file /core/jwt of the component JWT. The manipulation of the argument bearer results in input validation. This vulnerability is known as CVE-2026-73418. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability classified as problematic has been found in nextauthjs next-auth (affected version unknown). Affected is the function getToken of the file /core/jwt of the component JWT. The manipulation of the argument bearer with an unknown input leads to a input validation vulnerability. CWE is classifying the issue as CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. This is going to have an impact on availability. CVE summarizes:

NextAuth.js provides authentication for Next.js. Prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32, the exported getToken() helper in the next-auth/jwt and @auth/core/jwt modules can throw an uncaught exception when it reads a malformed Authorization: Bearer header. When no session cookie is present, getToken() URL-decodes the bearer value before validating it, and malformed percent encoding causes decodeURIComponent() to throw instead of treating the token as invalid. Because getToken() is commonly called in API routes, middleware, and server-side request handlers, a single unauthenticated request can trigger an unhandled exception in code paths that authenticate requests, causing a per-request denial of service without exposing tokens, sessions, or other data and without bypassing authentication. This issue is fixed in @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-73418 since 08/12/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 08/12/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• nextauthjs

Name

• next-auth

Website

• Product: https://github.com/nextauthjs/next-auth/

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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