External risk intelligence

Windows DHCP Server Heap Overflow Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-69845

DHCP servers are designed to operate within local network segments to assign IP addresses to clients. While reachable over a network, they are rarely exposed directly to the public internet and are typically protected behind internal network boundaries and firewalls in standard enterprise deployments.

Buffer Overflow

Microsoft Windows 10 1607

before 10.0.14393.9512before 10.0.17763.9245r2before 10.0.20348.5622before 10.0.26100.33438

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

A critical vulnerability has been identified in Windows DHCP Server, potentially allowing an unauthorized attacker to execute code remotely. This issue could have significant implications if exploited, as it affects a core network service responsible for IP address allocation. The primary concern at this stage is to confirm whether our environment utilizes this specific technology and assess any potential exposure.

Attackers could run code on affected systems.
Protects core network IP address services.
Confirm relevance and potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted network request to a vulnerable Windows DHCP server. This could be initiated from anywhere on the network, as the vulnerability is reachable without any prior authentication or specific user interaction. Successful exploitation could allow an unauthorized attacker to execute arbitrary code on the server.

Network access required.
Triggered by a crafted network request.
Enables unauthorized code execution.

Live Threat

Current exploitation, exposure, and threat context

An unauthenticated attacker could execute arbitrary code over a network by exploiting a heap-based buffer overflow in the Windows DHCP Server. This could impact the availability and integrity of affected systems when supported by the advisory.

Asset at risk: Windows DHCP Server systems.
Exposure: Network code execution.
Consequence: Potential system compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Windows DHCP Server requires immediate attention from infrastructure and security teams responsible for network services. The first critical step is to identify all DHCP server instances within your environment, determine their network exposure, and confirm their business criticality. Once identified, the accountable owner for each instance must be found to plan a risk-based remediation strategy, potentially involving vendor coordination or temporary mitigation if immediate patching is not feasible.

Network infrastructure teams own this issue.
Verify DHCP server network exposure and criticality.
Plan remediation based on risk assessment.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is Windows DHCP Server?

Windows DHCP Server is a foundational network service built into Windows Server operating systems. Its primary purpose is to automate the assignment of IP addresses and related network configuration parameters to devices—such as laptops, phones, and printers—when they connect to a network. By managing these addresses centrally, it ensures that devices can communicate without manual configuration, making it a critical component for stable internal network connectivity.

What does a heap-based buffer overflow mean for CVE-2026-69845?

This vulnerability involves a memory management error known as a heap-based buffer overflow (CWE-122). In plain terms, the server fails to properly check the size of incoming data before storing it in its memory (heap). An attacker can send a specially crafted request that exceeds the allotted space, overwriting adjacent memory. This corruption can disrupt the service or, more critically, allow the attacker to inject and execute their own malicious code on the server.

How is this Windows DHCP Server vulnerability triggered?

The vulnerability is triggered when an attacker sends a malformed network request to the DHCP service. Because the service is designed to process incoming requests from network clients, it does not require the attacker to have a valid account or interact with a user to initiate the attack. Crucially, this does not happen through standard, valid IP assignment traffic; it requires a specifically malicious packet designed to exploit the memory handling flaw.

How relevant is CVE-2026-69845 to my internal network?

According to Halo Surface Signal, this vulnerability is considered 'Unlikely' to be directly reachable from the public internet. Windows DHCP Servers are fundamentally designed to function within local network segments to serve internal clients. Because these servers are typically positioned behind firewalls and internal network boundaries rather than being exposed to the open web, the practical risk is generally lower for systems not directly accessible to external entities.

When should I take action to address this issue?

You should prioritize this immediately by identifying all servers running the DHCP role in your environment. Since this flaw allows unauthorized code execution, teams should catalog these assets, confirm their specific network placement, and determine their business importance. Once you have a list of active DHCP servers, you can work with the appropriate owners to schedule security updates or apply risk-mitigation strategies to protect these core infrastructure components.

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69845

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.