CVE-2026-73418

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.

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.

Summary

The exported getToken() helper (next-auth/jwt and @auth/core/jwt) 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 the decode step to throw rather than being treated as an invalid token. Because getToken() is commonly called in API routes, middleware, and other request handlers, a single unauthenticated request can trigger an unhandled exception in code paths that authenticate requests.

Am I affected?

You are affected if all of the following hold:

• You use next-auth <= 5.0.0-beta.25 (or @auth/core exposing the same getToken() implementation).
• Your application calls getToken() directly — for example in a Route Handler, middleware, or server-side request handler.
• You do not wrap that getToken() call in your own try/catch.

You are not affected if you only use the framework's auth() helper and never call getToken() yourself, or if every getToken() call site already has its own exception handling.

Impact

• Denial of service: an unauthenticated request carrying a malformed Bearer authorization header can raise an unhandled exception in any handler that calls getToken().
• The impact is per-request and limited to availability; it does not expose tokens, sessions, or other data, and does not bypass authentication.

CWE-20: Improper Input Validation.

Patched version

The fix makes getToken() treat a malformed Bearer value as an invalid token and return null, matching how other undecodable tokens are already handled. Upgrade to the first release containing this fix (to be published; this advisory will be updated with the exact patched version before publication) and no code changes are required.

Workarounds

If you cannot upgrade immediately, either:

• Config/code-level: wrap your getToken() calls so a thrown error is treated as "no token", e.g.

  let token = null
  try {
    token = await getToken({ req, secret })
  } catch {
    token = null
  }
  

• Or strip/normalize the incoming Authorization header at the edge (proxy, middleware) before it reaches getToken(), rejecting values whose Bearer portion is not valid percent-encoding.

Credit

Reported by @deprrous. Thank you for the responsible disclosure.

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.

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.

Summary

The exported getToken() helper (next-auth/jwt and @auth/core/jwt) 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 the decode step to throw rather than being treated as an invalid token. Because getToken() is commonly called in API routes, middleware, and other request handlers, a single unauthenticated request can trigger an unhandled exception in code paths that authenticate requests.

Am I affected?

You are affected if all of the following hold:

• You use next-auth <= 5.0.0-beta.25 (or @auth/core exposing the same getToken() implementation).
• Your application calls getToken() directly — for example in a Route Handler, middleware, or server-side request handler.
• You do not wrap that getToken() call in your own try/catch.

You are not affected if you only use the framework's auth() helper and never call getToken() yourself, or if every getToken() call site already has its own exception handling.

Impact

• Denial of service: an unauthenticated request carrying a malformed Bearer authorization header can raise an unhandled exception in any handler that calls getToken().
• The impact is per-request and limited to availability; it does not expose tokens, sessions, or other data, and does not bypass authentication.

CWE-20: Improper Input Validation.

Patched version

The fix makes getToken() treat a malformed Bearer value as an invalid token and return null, matching how other undecodable tokens are already handled. Upgrade to the first release containing this fix (to be published; this advisory will be updated with the exact patched version before publication) and no code changes are required.

Workarounds

If you cannot upgrade immediately, either:

• Config/code-level: wrap your getToken() calls so a thrown error is treated as "no token", e.g.

  let token = null
  try {
    token = await getToken({ req, secret })
  } catch {
    token = null
  }
  

• Or strip/normalize the incoming Authorization header at the edge (proxy, middleware) before it reaches getToken(), rejecting values whose Bearer portion is not valid percent-encoding.

Credit

Reported by @deprrous. Thank you for the responsible disclosure.