CVE-2026-69845 in Windows
Summary
by MITRE • 09/09/2026
Heap-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 identified as CVE-2016-3314 or similar variants depending on the specific patch cycle context. This issue stems from an improper handling of memory allocation and bounds checking during the processing of DHCP messages received over a network connection. When the DHCP server processes specially crafted packets, it fails to correctly validate the length of certain fields within the protocol data unit before copying them into heap-allocated buffers. This lack of rigorous input validation allows an attacker to write more data than the buffer can hold, resulting in a heap-based buffer overflow condition that corrupts adjacent memory structures on the server's heap space.
From a technical perspective, this flaw aligns with CWE-122, which defines Heap-Based Buffer Overflow as a type of vulnerability where a program writes data past the end or beginning of a heap allocation. The DHCP service operates continuously and listens for incoming requests from clients seeking network configuration parameters such as IP addresses, subnet masks, and default gateways. Because this service is often exposed to untrusted networks in enterprise environments, an attacker can exploit this weakness by sending maliciously formatted DHCP packets that trigger the overflow during parsing routines. By carefully crafting these payloads, a sophisticated adversary can overwrite critical heap metadata or function pointers stored within the same memory region as the buffer.
The operational impact of successfully exploiting this vulnerability is severe and potentially catastrophic for affected systems. An attacker who achieves successful exploitation gains the ability to execute arbitrary code with the privileges of the DHCP server process, which typically runs under high-privilege accounts such as SYSTEM or Network Service depending on the configuration. This level of access allows the adversary to install programs, view, change, or delete data, and create new accounts with full user rights. Furthermore, because the vulnerability can be triggered remotely without requiring any prior authentication, it represents a significant risk for automated worm propagation across vulnerable networks. The attacker does not need physical access or local account credentials, making this an attractive target for widespread network-based attacks aimed at establishing persistent footholds within corporate infrastructure.
In terms of threat modeling and industry standards, this vulnerability is closely associated with MITRE ATT&CK technique T1203, which covers Exploitation for Client Execution, as well as techniques related to remote code execution via protocol vulnerabilities such as those found in SMB or RPC services. The attack vector falls under Initial Access through Network Service Exploitation, allowing adversaries to bypass perimeter defenses if the DHCP server is accessible from untrusted zones. Defense-in-depth strategies are essential here; while network segmentation can limit exposure, it does not eliminate the risk entirely since internal traffic often traverses these segments freely.
Mitigation efforts primarily rely on applying vendor-supplied security updates that address the underlying memory management errors within the DHCP service codebase. Organizations must ensure that all Windows servers running the DHCP role are patched to versions where this heap overflow has been remediated through improved bounds checking and input validation routines. Additionally, network administrators should implement strict firewall rules to restrict access to the DHCP server ports (UDP 67 and UDP 68) only from trusted subnets or specific client ranges whenever possible. Deploying intrusion detection systems that can identify anomalous DHCP packet structures may also provide an additional layer of defense by detecting exploitation attempts in real-time before they result in successful code execution. Regular vulnerability scanning and continuous monitoring for unusual network activity related to DHCP traffic are recommended practices to maintain the integrity of the infrastructure against such remote exploits.