CVE-2024-38476 - Severe Vulnerability in Apache HTTP Server 2.4.59 and Earlier: Information Disclosure, SSRF, and Local Script Execution Risks

The Cybersecurity community has recently discovered a critical vulnerability in the core of Apache HTTP Server 2.4.59 and earlier versions. This vulnerability, identified as CVE-2024-38476, presents a severe risk of information disclosure, Server-Side Request Forgery (SSRF), and local script execution via malicious or exploitable response headers from backend applications.

This post will provide an in-depth analysis of this vulnerability, with code snippets and links to original references, and discuss its exploitation and potential impact. It is strongly recommended that users upgrade their Apache HTTP Server to version 2.4.60 to mitigate the risks associated with this vulnerability.

Vulnerability Description

In versions 2.4.59 and earlier of the Apache HTTP Server, a weakness in how response headers are processed has been identified. When handling response headers from backend applications, the server may not properly sanitize user input data, which could lead to the execution of unintended code or disclosure of sensitive information.

There are three main threats associated with this vulnerability

1. Information Disclosure: Attackers can manipulate response headers to reveal system or user information that could be used for further attacks.

2. SSRF: By crafting malicious headers, an attacker could cause the server to send requests to arbitrary internal or external systems, potentially gaining unauthorized access to sensitive resources or enabling other attacks.

3. Local Script Execution: Malicious headers could be used to execute code on the server, potentially compromising its security or stability.

Exploit Details

Although specific exploit details are not disclosed to protect the vulnerable systems, the general process involves sending crafted HTTP requests to the server that return malicious response headers. These headers could contain unsafe characters, directives, or values that, when processed by the server, would trigger the aforementioned threats.

Links to Original References

- Apache HTTP Server Project - Security Advisory: https://httpd.apache.org/security/vulnerabilities_24.html
- CVE-2024-38476 Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-38476

Code Snippet Example

The following is an example of a malicious header that could be sent by the backend application, which could lead to the vulnerability being exploited:

HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
X-Bad-Header: (); system("uname -a"); /* <-- Malicious payload here
...

In this example, the X-Bad-Header contains a malicious payload that would execute the "uname -a" command on the server, potentially revealing system information or allowing further exploitation.

Mitigation and Recommendations

The best way to mitigate this vulnerability is to upgrade to Apache HTTP Server 2.4.60, which fixes the issue. Users running earlier versions must ensure they apply all the latest security patches and follow proper configuration and deployment guidelines. Furthermore, users should monitor their server logs for unusual activity and employ best practices to ensure that backend applications do not generate exploitable response headers.

Conclusion

CVE-2024-38476 represents a severe vulnerability in the core of Apache HTTP Server 2.4.59 and earlier versions, with considerable risks of information disclosure, SSRF, and local script execution. Users are highly encouraged to upgrade their systems to version 2.4.60 to mitigate these risks.

Timeline

Published on: 07/01/2024 19:15:04 UTC
Last modified on: 08/21/2024 15:08:56 UTC