Apache Tomcat CGI Servlet Flaw Bypasses Security

A newly discovered security vulnerability, identified as CVE-2025-46701, has been found in Apache Tomcat’s CGI servlet implementation.

This flaw allows attackers to bypass configured security constraints under specific conditions, potentially exposing sensitive applications to unauthorized access.

What is the Vulnerability-CVE-2025-46701?

The problem arises from how Apache Tomcat handles case sensitivity in the URL path component known as pathInfo, which is part of the CGI servlet’s URL mapping. When Tomcat is running on a case-insensitive file system (common on Windows environments) and security constraints are applied to these URL paths, specially crafted URLs can circumvent those security measures.

This means attackers could potentially access restricted resources or execute commands that should be blocked by the server’s security settings.

Affected Versions

This vulnerability impacts multiple versions across three major Apache Tomcat branches:

• Versions 11.0.0-M1 through 11.0.6
• Versions 10.1.0-M1 through 10.1.40
• Versions 9.0.0-M1 through 9.0.104

Since CGI support is disabled by default in Apache Tomcat, only systems where CGI has been explicitly enabled are vulnerable. Typically, CGI is used in legacy applications or specific development scenarios, so many standard Tomcat deployments may not be affected.

Even though this vulnerability is classified as low severity, it poses a significant risk for organizations relying on CGI-based applications with strict access controls. Attackers exploiting this flaw could bypass these controls, potentially gaining unauthorized access or disrupting services.

How to Protect Your Systems

The Apache Software Foundation has responded quickly, releasing patched versions of Tomcat that address this issue:

• Apache Tomcat 11.0.7
• Apache Tomcat 10.1.41
• Apache Tomcat 9.0.105

These updates fix the case sensitivity issue in the CGI servlet, ensuring that security constraints cannot be bypassed in this way.

Recommended Actions:

1. Check if CGI is enabled on your Tomcat servers.
2. If CGI support is active, upgrade immediately to one of the patched versions listed above.
3. If CGI is not needed, ensure it remains disabled to reduce your attack surface.
4. Perform regular security audits and stay updated with Apache Tomcat’s security advisories.

While CGI may not be widely used in modern applications, legacy systems and specialized workflows still rely on it, making this vulnerability relevant to many enterprises. Regularly updating software and reviewing enabled features can greatly reduce security risks.

Stay informed, keep your servers patched, and protect your applications against evolving threats.