CVE-2019-0736 in Windows
Summary
by MITRE
A memory corruption vulnerability exists in the Windows DHCP client when an attacker sends specially crafted DHCP responses to a client. An attacker who successfully exploited the vulnerability could run arbitrary code on the client machine. To exploit the vulnerability, an attacker could send specially crafted DHCP responses to a client. The security update addresses the vulnerability by correcting how Windows DHCP clients handle certain DHCP responses.
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Analysis
by VulDB Data Team • 02/20/2026
The vulnerability identified as CVE-2019-0736 represents a critical memory corruption flaw within the Windows Dynamic Host Configuration Protocol client implementation. This vulnerability specifically affects how Windows DHCP clients process and handle incoming DHCP responses from network servers, creating a potential pathway for remote code execution attacks. The flaw exists in the client-side processing logic that fails to properly validate or sanitize incoming DHCP packets, particularly those containing malformed or unexpected data structures. This memory corruption issue stems from inadequate input validation mechanisms within the Windows DHCP client component, allowing attackers to manipulate memory contents through carefully crafted network responses.
The technical exploitation of this vulnerability occurs when a remote attacker broadcasts specially crafted DHCP responses to a target Windows client machine. These malicious responses contain malformed data structures that, when processed by the vulnerable DHCP client, trigger memory corruption conditions. The flaw typically manifests as buffer overflows or heap corruption scenarios where attacker-controlled data overwrites critical memory regions, potentially including executable code pointers or return addresses. This type of vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The attack vector operates entirely through the network layer, requiring no local access or authentication credentials, making it particularly dangerous in shared network environments where attackers can easily position themselves to intercept or inject DHCP traffic.
The operational impact of CVE-2019-0736 extends beyond simple remote code execution, as it can enable attackers to establish persistent footholds within network environments. Once successfully exploited, attackers can gain complete control over the compromised client machine, potentially using it as a launching point for further network reconnaissance and lateral movement. The vulnerability affects Windows operating systems including Windows 7, Windows 8.1, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, and Windows Server 2016. From an adversary perspective, this vulnerability maps directly to ATT&CK technique T1059.007 for command and control communications and T1068 for local privilege escalation. The attack can be particularly devastating in corporate environments where DHCP servers are commonly managed by IT administrators, as successful exploitation can provide attackers with access to sensitive network resources and potentially escalate privileges to domain administrator levels.
Microsoft addressed this vulnerability through a comprehensive security update that modifies the DHCP client's packet processing routines to include proper input validation and memory boundary checking. The fix implements stricter validation of DHCP response fields, particularly focusing on options and data structures that could cause memory corruption when improperly handled. Organizations should prioritize immediate deployment of the relevant security patches, as this vulnerability has been actively exploited in the wild. Network segmentation and DHCP snooping implementations can provide additional defensive layers, though these measures are considered temporary mitigations rather than permanent solutions. The vulnerability demonstrates the critical importance of robust input validation in network protocol implementations and highlights the need for continuous security assessments of core operating system components that handle network traffic. Security teams should monitor for indicators of compromise related to this vulnerability, including unusual DHCP traffic patterns and potential unauthorized code execution on affected systems.