A significant security vulnerability, listed as CVE-2024-24795, has been discovered in multiple modules of the widely-used Apache HTTP Server. The flaw, which involves HTTP response splitting, could potentially allow an attacker to inject malicious response headers into backend applications, resulting in an HTTP desynchronization attack. Exploiting this vulnerability can potentially lead to various adverse consequences, including information theft, malware injection, or website defacement.

In this post, we will dive deep into the details of this vulnerability, its potential impact, and the steps you can take to safeguard your Apache HTTP Server against it. We will provide code snippets and links to original references to help you better understand and mitigate this threat.

Consider the following example code snippet in an Apache HTTP Server configuration file

<Location "/">
  Header merge Set-Cookie "C=1; Path=/"
  RequestHeader unset C
  Header unset Set-Cookie C
</Location>

In this example, an attacker can execute an HTTP response splitting attack by sending a malicious request to the server. This request can cause the server to inject an additional 'Set-Cookie' header into the backend application, potentially leading to HTTP desynchronization or other harmful consequences.

Original References

The Apache Software Foundation published an official security advisory related to this vulnerability, CVE-2024-24795, on its website. You can view the full details of the advisory at the following link:

https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2024-24795

Exploit Details

The HTTP response splitting vulnerability exists due to improper handling of certain response headers by the Apache HTTP Server's affected modules. An attacker who is capable of injecting malicious response headers into backend applications can exploit this vulnerability to cause various security issues.

HTTP desynchronization is one prominent result of this exploit. Desynchronization occurs when the frontend and backend servers process a split HTTP response differently, allowing the attacker to smuggle requests, bypass security filters, or hijack user sessions. Moreover, attackers could use this vulnerability in phishing campaigns, leading to an increased risk for web users.

Mitigation

To address this vulnerability, users of Apache HTTP Server are recommended to upgrade their installations to version 2.4.59, which includes a fix for the issue. You can download the new version from the official Apache HTTP Server website at the following link:

http://httpd.apache.org/download.cgi

In addition to upgrading the server software, administrators should review their server configurations and ensure that response header manipulation modules are correctly configured to prevent response splitting.

Conclusion

The discovery of this major HTTP response splitting vulnerability, CVE-2024-24795, serves as a critical reminder of the importance of securing web infrastructure, especially when using prevalent server technologies like Apache HTTP Server. By ensuring that you stay up-to-date with security updates and patches, you can keep your web applications safe from various threats – including potentially disastrous exploits like the one discussed in this post.

Keep an eye on official security advisories from software vendors like the Apache Software Foundation, as they will provide timely updates and recommendations to help you keep your server and application environments secure.

Timeline

Published on: 04/04/2024 20:15:08 UTC
Last modified on: 07/30/2024 02:15:04 UTC