Category: Windows vulnerabilities

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EternalBlue vulnerability: Explained with POC

Hello, aspiring Ethical Hackers. In this article, you will learn about the infamous EternalBlue vulnerability and its exploitation.

Vulnerability & Impact

Exploited by Wannacry ransomware, the EternalBlue vulnerability exists in the Server Message Block (SMB) protocol. Due to improper handling of specially crafted packets by SMB version 1 (SMBV1) of Microsoft windows this vulnerability allows attackers to execute malicious code on the vulnerable systems. This vulnerability affects Microsoft Windows versions Windows Vista, Windows 7, Windows 8.1, Windows 10, Windows Server 2008, Windows Server 2012, Windows XP, Windows 8 and Windows Server 2003. This vulnerability was observed being exploited as recently as 2020.

Proof Of Concept

As the vulnerability is so famous (I mean infamous), Metasploit has already released exploit modules for this particular vulnerability.

We are going to test some of these modules on a Windows 7 target. Let’s first use the scanner module of metasploit to test whether this machine is vulnerable to EternalBlue vulnerability.

Set the RHOSTS option and execute the module.

The scanner module confirms that the target is indeed vulnerable. Now, let’s load the module for exploiting Eternal Blue vulnerability and grab a session.

Set all the required options and use “check” command to see if the target is indeed vulnerable.

After all the required options are set, execute the module.

eternalblue

As you can see, we got a meterpreter session on the target system and that too with SYSTEM privileges.

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Follina : Explained with POC

Hello aspiring Ethical Hackers. In this article, readers will learn about Follina, the latest Zero-Day vulnerability in Microsoft.

Vulnerability & Impact

Follina is the name given to a remote code execution (RCE) vulnerability in the Microsoft Support Diagnostic Tool (MSDT). This vulnerability allows a remote attacker to use a Microsoft Office document template to execute code via MSDT and download a malicious payload from a remote URL. It affects Office 2013, 2016, 2019, 2021, Office ProPlus and Office 365.

What actually is Follina?

Follina is a municipality that is located 60 kms northwest of Venice in Italy. Completely unrelated, the vulnerability has been named Follina as the malicious file was referencing to an executable that was named 0438. This is the area code of Follina, hence the zero-day has been named so.

What is MSDT?

Follina exploits MSDT but what is MSDT? Microsoft Support Diagnostic Tool (MSDT) is a service used for gathering diagnostic data about the system.

Proof Of Concept

Let’s see how to exploit Follina practically. For this let’s download a exploit from Github. Navigate into the cloned directory and you will files as shown below.

Two files are important in this directory. The “clickme.docx” is the file that uses MSDT to connect to a remote website and execute the exploit. The exploit is present in the “exploit.html” file. If this POC is successful, the exploit will popup calc.exe.

I tested this exploit on MS Office 2019 running on Windows 10. I hosted the exploit using Wamp server running on localhost.

I opened the clickme.doc and waited. Nothing happened. Then I saved it as clickme.rtf file as shown below.

This time when I clicked on clickme.rtf file, this happened,

And the calculator popped up. The Proof Of Concept Is Successful.

follina

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PrintNightmare, Privilege Escalation in Powershell

PrintNightmare is a critical vulnerability affecting the Microsoft Windows operating systems. The recently disclosed vulnerability is present in the print spooler service of Microsoft Windows. The printer spooler service is used for printing services and is turned on by default. The versions of Windows vulnerable to PrintNightmare include Windows 7 to Windows 10 and windows Server 2008 to the latest version of Windows Servers.

The PrintNightmare vulnerability has two variants : one is enabling remote code execution (CVE-2021-34527) and the other privilege escalation (CVE-2021-1675). In this article, readers will see a demonstration of exploiting the privilege escalation vulnerability in PrintNightmare.
For this demonstration, we will use Windows 10 version 1809. The Powershell Script we used in this demo can be downloaded from Github.

In this scenario, imagine I already have access to the target machine as a user with low privileges. Let me demonstrate it to you. The first thing I need to confirm is whether the printer spooler service is running on the target system or not. This can be done using powershell command “Get-Service -Name “spooler”“.

The print spooler service is running. Now I can exploit it. Before that let me show you that I am a user with limited privileges i.e as “user 1” with very limited privileges.

Next, I already downloaded the Powershell script I need to exploit the Printnightmare vulnerability .So I moved to the Downloads folder where the Powershell script is saved. Once I am inside that folder, I run the command

“Import-Module .\ <script Name>“as shown below.

Once the Powershell module is imported, I can execute the script with command
“Invoke-Nightmare -NewUser “<username to create >” -NewPassword <password for that new user> DriverName “PrintMe”“
This command will create a new user with administrator privileges.

How to exploit printnightmare

In the image above, you can see the existence of new user named “hacker” which I created. Now, let’s check the privileges of this user.

As readers can see, the new user I created belongs to the local administrators group. I reboot the system and try to login as that user.

The exploitation is successful.