CVE-2026-70201 in Windows
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Windows DHCP Server allows an authorized attacker to deny service locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified as an out-of-bounds read within the Microsoft Dynamic Host Configuration Protocol (DHCP) server represents a critical memory safety flaw that compromises the availability of network infrastructure services. This specific defect occurs when the DHCP server processes specially crafted packets or malformed configuration data, leading to an attempt to access memory locations outside the intended buffer boundaries. While typical out-of-bounds reads are often associated with information disclosure vulnerabilities where sensitive kernel or application memory contents might be leaked to an attacker, in this particular instance, the primary consequence is a denial of service condition rather than arbitrary code execution or data exfiltration. The flaw allows an authorized attacker operating within the local security context to trigger a crash or hang state in the DHCP server process, effectively disrupting its ability to lease IP addresses and manage network connectivity for clients on the subnet.
From a technical perspective, this vulnerability falls under the category of CWE-125, which describes Out-of-bounds Read vulnerabilities where software reads data past the end, or before the beginning, of the intended buffer. The DHCP server service in Windows is responsible for dynamically assigning IP addresses and other network configuration parameters to devices on an IPv4 network. When a client requests these services, it sends specific request packets that are parsed by the server application. If the parsing logic fails to adequately validate the length or structure of incoming data fields before accessing them, the application may attempt to read from invalid memory addresses. This improper validation leads to undefined behavior within the operating system's kernel or service process, typically resulting in an access violation exception that causes the DHCP Server service (DHCPSVC) to terminate unexpectedly or become unresponsive.
The operational impact of this vulnerability is significant for organizations relying on automated network configuration. A successful exploitation results in a local denial of service against the DHCP server role hosted on the affected Windows system. This means that new devices joining the network will fail to obtain IP addresses, and existing leases may not be renewed properly if the service fails during lease management operations. For environments where the DHCP server is also hosting critical infrastructure services or acting as an authoritative source for a large number of clients, this disruption can lead to widespread connectivity issues, preventing users from accessing internal resources or external internet services until the service is manually restarted by an administrator. The requirement for local access and authorization limits the attack vector but does not diminish the severity for insider threats or compromised user accounts within the domain.
In terms of threat modeling and industry standards, this vulnerability aligns with MITRE ATT&CK technique T1499, Endpoint Denial of Service, specifically under sub-techniques involving resource exhaustion or service disruption through application crashes. It also relates to CWE-20, Improper Input Validation, as the root cause lies in the failure to sanitize and verify input data before processing. Security analysts should note that while remote exploitation is not possible due to the local access requirement, lateral movement within a network could leverage this vulnerability if an attacker gains foothold on a machine hosting the DHCP server role via other means such as phishing or credential theft.
Mitigation strategies primarily involve applying the latest security updates provided by Microsoft for the affected Windows versions. Organizations should ensure that their patch management processes are up to date, prioritizing patches related to network services and core operating system components. Additionally, implementing strict access controls is essential; administrators must enforce the principle of least privilege to minimize the number of users with local administrative rights or permissions to interact directly with DHCP server configurations. Network segmentation can also help isolate critical infrastructure servers from general user workstations, reducing the attack surface available to potential insiders who might attempt to exploit this flaw. Monitoring system logs for unexpected service restarts or application crashes in the Windows Event Viewer under System and Application logs related to DHCPSVC can aid in detecting attempted exploitation activities before they cause prolonged outages.