Critical Next.js Vulnerability: CVE-2025-29927

Overview

A critical security vulnerability, identified as CVE-2025-29927, has been discovered in Next.js, a popular React framework. This flaw allows attackers to bypass middleware-based authorization checks, potentially granting unauthorized access to restricted areas of applications. The vulnerability affects Next.js versions 11.1.4 through 15.2.2. :contentReference[oaicite:0]{index=0}

Details of the Vulnerability

The issue stems from the misuse of the internal HTTP header x-middleware-subrequest. Originally designed to prevent middleware from processing the same request multiple times, a design flaw permits external attackers to manipulate this header, effectively bypassing security checks implemented in the middleware. :contentReference[oaicite:1]{index=1}

Impact

Exploiting this vulnerability could allow unauthorized access to sensitive sections of a Next.js application, such as administrative dashboards or user data. This poses significant security risks, including data breaches and unauthorized operations. :contentReference[oaicite:2]{index=2}

Affected Versions

The vulnerability affects Next.js versions from 11.1.4 through 15.2.2. Applications using middleware for authorization or security checks are particularly at risk. :contentReference[oaicite:3]{index=3}

Mitigation Steps

To address this issue, Next.js has released patches in the following versions:

  • 15.x: Update to 15.2.3
  • 14.x: Update to 14.2.25
  • 13.x: Update to 13.5.9
  • 12.x: Update to 12.3.5

Developers are strongly encouraged to update their Next.js applications to the latest patched versions immediately. :contentReference[oaicite:4]{index=4}

Recommendations

  • Immediate Update: Upgrade to the patched versions as listed above.
  • Review Middleware Usage: Examine your application's middleware to ensure no unauthorized access is possible.
  • Monitor for Unusual Activity: Keep an eye on application logs for any signs of unauthorized access attempts.

Staying updated with the latest security patches is crucial to protect your applications from potential exploits.

References