Next.js Vulnerability: Critical Flaw Allows Authorization Bypass
TL;DR
A critical security vulnerability in the Next.js React framework could potentially be exploited to bypass authorization checks. This flaw, tracked as CVE-2025-29927, carries a CVSS score of 9.1 out of 10.0. The issue arises from how Next.js handles internal headers, specifically x-middleware-subrequest, which are used to prevent recursive requests from triggering infinite loops.
Critical Next.js Vulnerability Allows Authorization Bypass
Overview
A critical security vulnerability has been disclosed in the Next.js React framework, which could potentially be exploited to bypass authorization checks under certain conditions. The flaw, tracked as CVE-2025-29927, carries a CVSS score of 9.1 out of 10.0, indicating a severe security risk.
Technical Details
Next.js uses an internal header, x-middleware-subrequest, to prevent recursive requests from triggering infinite loops. However, this mechanism has been found to be vulnerable to manipulation, allowing attackers to bypass authorization checks. This vulnerability could enable unauthorized access to sensitive data or functionalities within applications built on Next.js.
Implications
The implications of this vulnerability are significant, particularly for enterprises and developers relying on Next.js for building secure web applications. Potential risks include:
- Unauthorized access to sensitive data
- Compromised user accounts
- Potential data breaches
Mitigation
To mitigate this vulnerability, it is crucial for developers to update to the latest version of Next.js, which includes patches for this security flaw. Additionally, implementing robust security practices such as regular code audits, penetration testing, and adhering to best practices for secure coding can help prevent such vulnerabilities.
Additional Resources
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Conclusion
The discovery of this critical vulnerability in Next.js underscores the importance of continuous security monitoring and prompt patch management. As Next.js continues to be a popular choice for developing React-based web applications, staying vigilant about security updates is essential for maintaining the integrity and security of web applications.