In early 2024, the security world was shaken by the emergence of a critical vulnerability known as CVE-2024-26195. This flaw affects Microsoft's DHCP Server service, providing attackers with a dangerous avenue for remote code execution—potentially letting them take over vulnerable systems on your network. In this long-read exclusive, we’ll break down how this vulnerability works, offer practical code snippets for testing, and guide you through protecting your environment. Let’s get started!

What Is CVE-2024-26195?

CVE-2024-26195 is a remote code execution (RCE) vulnerability discovered in the Microsoft DHCP Server service. In simple terms, it allows attackers on the same network to run any code they want on your unpatched Windows DHCP server—without the need for authentication. That means full control.

Microsoft addressed this in their March 2024 Patch Tuesday update. Ignoring the patch could leave your systems open to attacks leading to data theft, ransomware, or total system compromise.

Reference:
- Microsoft Security Update Guide: CVE-2024-26195
- NVD - National Vulnerability Database Entry

How The Attack Works

The core of CVE-2024-26195 lies in how the DHCP Server service parses and handles certain crafted network packets. By sending a specially crafted DHCP request, an attacker can trigger a memory corruption bug—usually a buffer overflow—which then lets them execute code of their choice on the server.

Attacker crafts malicious DHCP packets.

3. Packets are sent to the server, causing memory corruption and opening the door to malicious code running as SYSTEM.

Code Example: Simulating A Malicious DHCP Packet

*Disclaimer: This example is for educational purposes only. Do not use it to attack any system you do not own or have express permission to test.*

This Python snippet uses scapy to build a non-standard DHCP request packet. While this won’t exploit the vulnerability, it’s a template that researchers might build on for testing packet handling:

# Install scapy with: pip install scapy
from scapy.all import *

# Craft a DHCP Discover packet with oversized Option field to trigger potential buffer
packet = (Ether(dst="ff:ff:ff:ff:ff:ff") /
          IP(src="...", dst="255.255.255.255") /
          UDP(sport=68, dport=67) /
          BOOTP(chaddr=RandMAC()) /
          DHCP(options=[
              ("message-type", "discover"),
              ("hostname", "A" * 300), # Deliberately oversize hostname option
              "end"
          ]))

sendp(packet, iface="eth", verbose=1)

In a real-world attack, the payload would be designed to overflow the memory and hijack execution flow, but Microsoft has kept specific exploit details under wraps.

Proof of Concept: What Might An Exploit Look Like?

Security researchers hint that a workable exploit can be assembled with deep DHCP protocol knowledge and reverse engineering.

General Exploit Flow

1. Craft and send a DHCP request/response with oversized options (e.g., hostname, vendor-specific info).

Payload runs with SYSTEM privileges, often opening a reverse shell or dropping malware.

*The actual buffer or option type used for the overflow may change based on the server version and patch status.*

Patch Immediately:

Download and install the latest updates from Microsoft. The fix for CVE-2024-26195 is included in March 2024’s security bundle.

Intrusion Detection:

Monitor for suspicious DHCP traffic using IDS/IPS tools. Set alerts on abnormal packet sizes or malformed requests.

Disabling Unused DHCP:

If you’re not using DHCP server features, disable the service entirely or run it on a hardened dedicated system.

Check these resources for deeper technical detail

- Microsoft Security Response Center (MSRC) Advisory
- DHCP RFC 2131
- Exploit Database - DHCP Server Attacks

Summary

CVE-2024-26195 is a sober reminder that network infrastructure remains a hot target—especially unauthenticated services like DHCP. The lesson? Patch quickly, audit your network, and keep a close eye on the traffic to critical services. Even a single overlooked server can put your environment at risk.

Stay informed, stay updated, and stay secure.

*Original content by [Your Security Blog Name]. For requests or more info, contact us or follow on [LinkedIn/Twitter].*

Timeline

Published on: 04/09/2024 17:15:37 UTC
Last modified on: 04/10/2024 13:24:00 UTC