Summary: A security vulnerability has been discovered in the mod_proxy module of Apache HTTP Server versions 2.4.59 and earlier. This vulnerability, tracked as CVE-2024-38473, is related to an encoding problem that allows attackers to send request URLs with incorrect encoding to backend services, potentially bypassing authentication via crafted requests. Users of Apache HTTP Server are advised to upgrade to version 2.4.60, which addresses this issue.

What is mod_proxy?

mod_proxy, a module in Apache HTTP Server, is primarily responsible for reverse proxy and load balancing tasks, allowing requests to be forwarded to backend servers. By doing so, mod_proxy helps distribute the load among multiple servers, streamlining the request processing and increasing the availability and scalability of the overall system.

Vulnerability Details: CVE-2024-38473

A security researcher recently identified a vulnerability in mod_proxy, affecting Apache HTTP Server versions 2.4.59 and earlier. This vulnerability stems from an encoding issue that enables request URLs with incorrect encoding to be sent to backend services. Consequently, an attacker can craft a request that bypasses the authentication mechanism, potentially gaining unauthorized access to the targeted services.

An attacker could exploit CVE-2024-38473 by crafting a malicious request as shown below

<?php
// Crafted malicious request
$malicious_request = "GET /path/%2e%2e/secret_file HTTP/1.1";

// Send the request to the vulnerable server
$result = send_request($malicious_request);

// Process the response and check if authentication is bypassed
if (is_authentication_bypassed($result)) {
    echo "Authentication bypassed!";
}
?>

This example demonstrates a situation in which an attacker creates a request containing an encoded path traversal sequence in the URL (%2e%2e). If the targeted server is vulnerable to the encoding issue in mod_proxy, such a request may lead to the bypass of the authentication process.

- Apache HTTP Server official announcement

http://httpd.apache.org/security/vulnerabilities_24.html

- CVE information from the National Vulnerability Database (NVD)

https://nvd.nist.gov/vuln/detail/CVE-2024-38473

Solution and Patch Information

To mitigate the CVE-2024-38473 vulnerability and protect your server from potential attacks, it is crucial to upgrade your Apache HTTP Server installation to version 2.4.60 or later. The latest version of the software contains a patch that addresses the encoding issue in mod_proxy.

You can download Apache HTTP Server version 2.4.60 from the official Apache download page

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

For users who cannot immediately upgrade their installations, it may be advisable to implement strict access controls and robust monitoring for suspicious activities on the servers.

In conclusion, the CVE-2024-38473 vulnerability in mod_proxy of Apache HTTP Server exposes servers running on versions 2.4.59 and earlier to potential attacks, enabling attackers to send request URLs with incorrect encoding to backend services, potentially bypassing authentication and gaining unauthorized access. To protect your systems, it is highly recommended to upgrade to Apache HTTP Server 2.4.60 or apply alternative mitigation measures.

Timeline

Published on: 07/01/2024 19:15:04 UTC
Last modified on: 08/01/2024 13:54:52 UTC