External risk intelligence

Windows DHCP Server Heap-Based Buffer Overflow Remote Code Execution

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-56159

The Windows DHCP Server is a network-layer service. While it is network-reachable, it is typically deployed within internal network segments or behind firewalls to serve local clients and is not designed or intended to be exposed directly to the public internet.

Buffer Overflow

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability in Windows DHCP Server could allow an unauthorized attacker to execute code remotely. The primary concern is to confirm whether this technology is relevant to our environment and assess any potential exposure.

Vulnerability allows remote code execution.
Verify relevance and potential exposure.
Confirm if our DHCP servers are affected.

Attack Path

How an attacker could exploit the issue

An attacker can exploit this vulnerability by sending specially crafted network requests to the Windows DHCP Server, which is accessible over a network. This could allow an unauthorized attacker to execute arbitrary code on the affected server, potentially leading to a complete system compromise.

No privileges or user interaction needed.
Triggered by network requests to DHCP Server.
Leads to unauthorized code execution.

Live Threat

Current exploitation, exposure, and threat context

An attacker could execute arbitrary code over a network by exploiting a heap-based buffer overflow in the Windows DHCP Server. This could affect the availability and integrity of the affected server, and potentially allow for further compromise of the network.

Server code execution
Network code execution
Service disruption or control

Operational Fix

Recommended remediation, mitigation, and detection steps

This critical vulnerability in Windows DHCP Server presents a significant risk, allowing for remote code execution over a network. Given the nature of DHCP services, infrastructure and network security teams are typically responsible for its management and security. The first practical step is to identify all instances of Windows DHCP Server within your environment, assess their network reachability and business criticality, and then locate the accountable owner to plan remediation.

Infrastructure and network teams own this.
Verify DHCP server network exposure.
Plan coordinated remediation efforts.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Windows DHCP Server?

Windows DHCP Server is a core network service that automatically assigns IP addresses and configuration parameters to devices on a network. It acts as the traffic controller for network identity, ensuring that computers, printers, and other devices can communicate properly by managing the address pool and providing essential connectivity details to clients.

What does CVE-2026-56159 mean for system memory?

This vulnerability is a heap-based buffer overflow, classified as CWE-122. It happens when the software writes more data to a specific memory area—the heap—than it is designed to hold. Because the DHCP service manages incoming requests, an attacker can manipulate this memory space to overwrite adjacent data, which can crash the service or allow the attacker to run their own unauthorized instructions.

How is this heap-based buffer overflow triggered?

An attacker triggers this bug by sending specially crafted network packets to the DHCP service. Importantly, this does not require the attacker to have pre-existing credentials or trick a human user into clicking something. If the service receives malformed data that exceeds its allocated buffer, the overflow occurs automatically during the processing of that request.

Is my server at risk if it is behind a firewall?

According to Halo Surface Signal, this service is usually deployed within internal network segments rather than the public internet. While the vulnerability is network-reachable, its risk is often mitigated by the fact that DHCP servers are typically shielded by internal segmentation. You should focus on servers that are reachable from untrusted network segments.

How do I start managing this Windows DHCP Server risk?

Begin by creating a definitive inventory of all systems running the Windows DHCP Server role in your environment. Once identified, evaluate which of these systems are reachable from sensitive or untrusted network zones. Identify the infrastructure teams responsible for these servers so you can coordinate with them to verify if patches or service configuration adjustments are available.

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56159

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.