CVE-2026-73418 nextauthjs CVE debrief

Who should care

Defenders responsible for NextAuth.js deployments should assess exposure and prioritize verification and updates to fixed versions. This includes reviewing and updating API routes, middleware, and server-side request handlers to handle exceptions and monitoring for potential denial of service attacks.

Why it matters

CVE-2026-73418 vulnerability in NextAuth.js can cause denial of service, requiring defenders to verify and update to fixed versions.

• Potential denial of service due to unhandled exceptions
• Need to verify and update to fixed versions of @auth/core and next-auth
• Review and update API routes, middleware, and server-side request handlers to handle exceptions

Technical summary

The exported getToken() helper in next-auth/jwt and @auth/core/jwt modules can throw an uncaught exception when reading a malformed Authorization: Bearer header, potentially leading to a denial of service. This occurs when getToken() URL-decodes the bearer value before validating it, and malformed percent encoding causes decodeURIComponent() to throw. The exception can occur in API routes, middleware, and server-side request handlers, leading to a per-request denial of service without exposing tokens, sessions, or other data and without bypassing authentication.

Defensive priority

Defenders should prioritize verifying and updating to fixed versions of @auth/core and next-auth to prevent potential denial of service.

Recommended defensive actions

• Verify and update to fixed versions of @auth/core and next-auth
• Review and update API routes, middleware, and server-side request handlers to handle exceptions
• Monitor for potential denial of service attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description and potential impact. The vulnerability is fixed in @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32. Defenders should verify and update to fixed versions to prevent potential denial of service. The CVE record was published on 2026-08-12T21:17:40.890Z and has not been modified since then.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.