CVE-2026-64641 in Next.js
Summary
by MITRE • 07/27/2026
Next.js is a React framework for building full-stack web applications. In versions 13.0.0 through 15.5.20 and 16.0.0 through 16.2.10, crafted requests targeting Next.js applications using App Router with at least one Server Action can lead to excessive CPU usage blocking processing of further requests in the same process. This issue has been fixed in versions 15.5.21 and 16.2.11.
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Analysis
by VulDB Data Team • 07/27/2026
This vulnerability affects Next.js applications utilizing the App Router with Server Actions, creating a denial of service condition through crafted requests that consume excessive CPU resources. The flaw manifests when specific request patterns are processed by the server-side rendering pipeline, causing the application to become unresponsive to subsequent requests within the same process. The vulnerability impacts a broad range of Next.js versions including 13.0.0 through 15.5.20 and 16.0.0 through 16.2.10, representing significant portions of the framework's adoption across production environments.
The technical root cause involves improper handling of request processing within the Server Actions execution context, where maliciously crafted requests can trigger computational overhead that blocks concurrent request processing. This occurs due to insufficient input validation and resource management during the server-side action execution flow, allowing attackers to consume CPU cycles beyond normal operational limits. The vulnerability is particularly dangerous because it affects the core App Router functionality and Server Actions mechanism, which are fundamental components in modern Next.js application architectures.
From an operational perspective, this vulnerability creates a severe availability risk for Next.js applications, potentially allowing attackers to render services unusable through sustained resource exhaustion attacks. The impact extends beyond simple performance degradation to complete service blocking, affecting all users of the affected application during the attack window. Organizations running Next.js applications with Server Actions are particularly vulnerable since these components are commonly used in modern web applications requiring server-side processing capabilities.
The mitigation strategy involves upgrading affected Next.js versions to 15.5.21 or 16.2.11, which contain the necessary patches addressing the CPU consumption issue. Additionally, implementing rate limiting mechanisms and request validation at the application level can provide additional protective layers against exploitation attempts. Security teams should also monitor their applications for unusual CPU usage patterns that might indicate exploitation attempts. This vulnerability aligns with CWE-400 - Uncontrolled Resource Consumption and relates to ATT&CK technique T1499.004 - Endpoint Denial of Service, emphasizing the need for robust resource management and input validation in web application frameworks.