CVE-2026-69620 in Windows
Summary
by MITRE • 09/09/2026
Stack-based buffer overflow in Windows DHCP Server allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described constitutes a critical security flaw within the Dynamic Host Configuration Protocol (DHCP) server service on Microsoft Windows operating systems, specifically manifesting as a stack-based buffer overflow. This type of memory corruption error occurs when a program writes more data to a fixed-length block of memory stored on the call stack than it is allocated to hold. In the context of the DHCP server, this flaw typically arises during the processing of specially crafted network packets that contain malformed or excessively long option fields. When the service attempts to parse these inputs without adequate bounds checking, the excess data overwrites adjacent memory locations on the stack, potentially including critical control structures such as return addresses and saved frame pointers. This overwrite allows an attacker to redirect the execution flow of the vulnerable process, thereby achieving arbitrary code execution with the privileges of the DHCP server service, which often runs under high-privilege accounts like SYSTEM or NETWORK SERVICE.
From a technical perspective, this vulnerability aligns closely with Common Weakness Enumeration (CWE) identifiers such as CWE-121, which describes stack-based buffer overflow, and potentially CWE-787 if it involves out-of-bounds write operations that corrupt memory structures beyond the immediate stack frame. The exploitation mechanism relies on the DHCP server's role in network infrastructure, where it automatically assigns IP addresses and other configuration parameters to clients. Because this service must process incoming requests from a wide range of sources, including untrusted networks, an attacker positioned within the same broadcast domain or with routed access can send maliciously crafted DHCP packets directly to the vulnerable host. The lack of rigorous input validation in older versions of the Windows implementation allows these packets to trigger the overflow condition during routine request handling procedures.
The operational impact of this vulnerability is severe due to its remote exploitability and high privilege level. An unauthorized attacker who successfully exploits this flaw can execute arbitrary code on the target system, effectively gaining full control over the affected machine. This compromise enables a wide array of malicious activities, including the installation of backdoors, deployment of malware such as ransomware or cryptominers, creation of persistent access points for further lateral movement within the network, and exfiltration of sensitive data stored on the compromised host. Furthermore, because DHCP is fundamental to network connectivity, compromising this service can also facilitate man-in-the-middle attacks by allowing the attacker to manipulate DNS settings or gateway configurations assigned to other clients, thereby disrupting network integrity and availability across a broader segment of the organization's infrastructure.
In terms of threat modeling and adversary behavior, this vulnerability maps directly to MITRE ATT&CK techniques related to initial access and execution. Specifically, it corresponds to T1059 Command and Scripting Interpreter if the attacker uses scripts for post-exploitation activities following successful code execution, or more broadly to remote exploitation vectors that do not require user interaction. The ability to execute code over a network without authentication makes this a high-severity threat vector often targeted by automated scanning tools and advanced persistent threats seeking quick footholds in enterprise environments. Attackers may leverage known exploit kits or custom payloads designed specifically for the DHCP stack overflow condition to achieve initial access before escalating privileges further through other local vulnerabilities if necessary.
Mitigation strategies must prioritize immediate patching of all affected Windows systems with the latest security updates provided by Microsoft, which include fixes that enforce proper bounds checking and input validation within the DHCP server service code path. Organizations should also implement network segmentation to restrict direct IP connectivity between untrusted networks and critical infrastructure servers hosting DHCP services. Additionally, deploying intrusion detection or prevention systems capable of identifying malformed DHCP packets can provide an additional layer of defense by blocking exploit attempts before they reach the vulnerable application logic. Regular auditing of network configurations and disabling unnecessary network services further reduces the attack surface, ensuring that only authorized traffic is processed by sensitive system components like the DHCP server.