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CVE-2026-23869 Summary

·2026.04.08 16:00

Key point

A CVSS 7.5 vulnerability in Next.js App Router has been disclosed, requiring immediate patch upgrades.

Details

A high-severity vulnerability with CVSS 7.5 has been found in React Server Components, which can lead to Denial of Service in unpatched environments.

Sending a specifically crafted HTTP request to an App Router Server Function endpoint and deserializing it can cause excessive CPU usage. If the attack succeeds, the service may slow down or stop.

The affected scope includes Next.js 13.x, 14.x, 15.x, 16.x and related packages using App Router. This issue is being tracked in the upstream repository as CVE-2026-23869.

Mitigations have already been deployed. New blocking rules have been applied to Vercel WAF, and protections have been rolled out across the platform worldwide, but WAF alone is not sufficient.

  • Users should immediately upgrade to the latest patched versions of React and affected sub-frameworks.
  • WAF is only a secondary line of defense and should not be relied upon as complete protection.
  • The updated releases include fixes that block this vulnerability.
vercelreactnextjswafreact-server-componentsapp-routercve-2026-23869denial-of-service
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