CVE-2026-69847 in Windows
Summary
by MITRE • 09/09/2026
Heap-based buffer overflow in Windows DHCP Server allows an authorized attacker to execute code over an adjacent network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified involves a heap-based buffer overflow within the Dynamic Host Configuration Protocol (DHCP) server service on Microsoft Windows operating systems. This specific flaw arises from improper validation of user-supplied input during the processing of DHCP messages, particularly those related to lease renewals or address assignments. When the DHCP server processes these requests, it allocates memory buffers to handle incoming data structures without sufficiently verifying their boundaries against expected limits. An attacker positioned on an adjacent network segment can craft a maliciously formatted DHCP packet containing oversized fields that exceed the allocated buffer size. Upon receipt and processing by the vulnerable service, this overflow allows arbitrary data to be written beyond the intended memory region, potentially overwriting critical heap metadata or function pointers stored in adjacent memory locations.
From a technical perspective, this flaw is classified under CWE-122, which denotes a heap-based buffer overflow. The exploitation mechanism relies on precise control of the overwritten memory contents to achieve arbitrary code execution. By carefully crafting the payload within the DHCP packet, an attacker can manipulate the return address or function pointer in the heap structure. When the compromised routine attempts to resume normal operation after handling the malicious request, it jumps to the attacker-controlled address rather than the legitimate next instruction. This transition grants the attacker the ability to execute arbitrary code with the privileges of the DHCP service account, which typically runs under SYSTEM-level permissions on Windows servers. The requirement for an adjacent network position implies that physical or logical proximity to the target subnet is necessary, as standard routing protocols may prevent direct delivery of crafted Layer 2 frames from distant networks unless specific conditions like ARP spoofing are employed.
The operational impact of this vulnerability is severe due to its potential for remote code execution without user interaction. Once exploited, an attacker gains full control over the affected DHCP server, which serves as a critical infrastructure component managing IP address allocation and network configuration parameters. This access can be leveraged to pivot into other parts of the internal network by modifying DNS records or routing tables managed through the compromised system. Furthermore, since the vulnerability affects core networking services, it disrupts normal network operations if exploited destructively, leading to denial of service conditions for clients relying on dynamic IP assignment. The ability to execute code remotely makes this a high-severity threat that requires immediate attention from security teams responsible for maintaining network infrastructure integrity.
In terms of industry frameworks, this vulnerability aligns with MITRE ATT&CK techniques related to initial access and privilege escalation via exploited components in the Network Service category. Specifically, it reflects patterns seen in attacks where attackers target common services running on default ports or protocols that are often left unpatched due to perceived low risk from external networks. The adjacent network requirement places this within the context of lateral movement scenarios where an attacker has already breached a perimeter segment and seeks to expand their foothold by compromising critical internal services like DHCP, DNS, or Active Directory Domain Controllers.
Mitigation strategies should prioritize immediate patching using official updates provided by Microsoft for all affected Windows versions. Organizations must ensure that their vulnerability management processes include regular scanning of network-facing services to identify unpatched systems promptly. Additionally, implementing strict access control lists on firewall rules can restrict DHCP traffic sources to only authorized subnets or specific IP ranges known to be legitimate clients. Network segmentation should also be reviewed to minimize the attack surface presented by critical infrastructure components like DHCP servers, ensuring they are not directly accessible from less trusted network zones without appropriate inspection and filtering mechanisms in place.