CVE-2021-43803 : Security Advisory and Response

Next.js is a React framework that experienced an unexpected server crash vulnerability in versions prior to 11.1.3 and 12.0.5. This vulnerability could lead to server crashes when encountering invalid URLs.

Understanding CVE-2021-43803

Next.js versions below 11.1.3 and 12.0.5 were susceptible to server crashes caused by invalid URLs, affecting deployments using Node.js above 15.0.0 and Next.js above 11.1.0.

What is CVE-2021-43803?

Next.js versions before 11.1.3 and 12.0.5 were prone to server crashes triggered by invalid or malformed URLs, potentially impacting application availability.

The Impact of CVE-2021-43803

CVSS Base Score: 7.5 (High)
Attack Vector: Network
Availability Impact: High
Attack Complexity: Low
Next.js deployments using versions susceptible to this issue could experience unexpected server crashes.

Technical Details of CVE-2021-43803

In-depth details about the vulnerability, affected systems, and exploitation mechanisms.

Vulnerability Description

The vulnerability arises from improper handling of invalid URLs, leading to server crashes in affected Next.js versions.

Affected Systems and Versions

Product: Next.js
Vendor: Vercel
Affected Versions: >= 11.1.0, < 11.1.3 and >= 12.0.0, < 12.0.5

Exploitation Mechanism

Attackers could exploit this issue by sending specially crafted invalid URLs to the server, causing it to crash and potentially disrupt services.

Mitigation and Prevention

Protecting systems against CVE-2021-43803 through immediate actions and long-term security practices.

Immediate Steps to Take

Update Next.js deployments to versions 11.1.3 or 12.0.5 containing patches for this vulnerability.
Implement input validation mechanisms to prevent malformed URLs from crashing the server.

Long-Term Security Practices

Regularly monitor and update dependencies to ensure using the latest secure versions.
Conduct security assessments and audits to identify and address potential vulnerabilities.

Patching and Updates

Ensure timely application of patches and updates for Next.js to mitigate known vulnerabilities.