CVE-2019-0726 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, aka 'Windows DHCP Client Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2019-0697, CVE-2019-0698.
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Analysis
by VulDB Data Team • 07/12/2024
The vulnerability described in CVE-2019-0726 represents a critical memory corruption flaw within the Windows Dynamic Host Configuration Protocol client implementation that enables remote code execution through malicious DHCP responses. This vulnerability specifically affects the Windows DHCP client component responsible for processing DHCP offers and acknowledgments from network servers, creating a pathway for attackers to exploit memory handling inconsistencies during DHCP message processing. The flaw manifests when the client receives specially crafted DHCP responses that contain malformed or unexpected data structures, leading to improper memory management and potential code execution privileges. The vulnerability operates at the network protocol level where Windows clients process DHCP communications, making it particularly dangerous in environments where clients automatically accept DHCP responses from any available server on the network.
The technical root cause of this vulnerability stems from inadequate input validation and memory management within the Windows DHCP client's response processing logic. When the client encounters malformed DHCP options or unexpected data within DHCP response packets, the parsing routines fail to properly validate buffer boundaries and memory allocation parameters. This leads to memory corruption conditions that can be exploited to overwrite critical memory locations, potentially allowing attackers to execute arbitrary code with the privileges of the affected Windows user account. The vulnerability falls under CWE-121, which describes "Stack-based Buffer Overflow" conditions, and CWE-122, which covers "Heap-based Buffer Overflow" scenarios, as the memory corruption can occur in both stack and heap memory regions during DHCP message processing. The attack vector requires the target system to be configured to automatically accept DHCP responses, typically in default network configurations where clients trust DHCP servers without additional validation mechanisms.
The operational impact of CVE-2019-0726 extends beyond individual system compromise to potentially enable broader network infiltration and lateral movement within corporate environments. An attacker positioned on the same network segment can exploit this vulnerability to gain remote code execution privileges on Windows clients, potentially escalating to domain administrator privileges if the compromised system has elevated access rights. The vulnerability affects multiple Windows operating systems including Windows 7, Windows 8.1, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, and Windows Server 2016, creating widespread exposure across enterprise networks where these systems are prevalent. The exploitability of this vulnerability is enhanced by the fact that Windows DHCP clients automatically process and accept DHCP responses without requiring explicit user interaction or authentication, making it particularly dangerous in unsecured network environments where attackers can easily position themselves to intercept DHCP communications.
Mitigation strategies for CVE-2019-0726 should focus on both immediate patching and network-level defensive measures to protect against exploitation attempts. Microsoft released security update MS19-034 that addresses this vulnerability through improved input validation and memory management within the DHCP client component, requiring administrators to apply the patch promptly across all affected systems. Network administrators should implement DHCP snooping and DHCP server authentication mechanisms to prevent unauthorized DHCP servers from operating on the network, effectively blocking potential attackers from crafting malicious responses that could exploit this vulnerability. Additional defensive measures include configuring Windows clients to disable automatic DHCP configuration when possible, implementing network segmentation to isolate critical systems from general network traffic, and deploying intrusion detection systems to monitor for unusual DHCP activity patterns. From an ATT&CK framework perspective, this vulnerability maps to technique T1059.007 for command and control communications and T1068 for exploit for privilege escalation, as the initial compromise can lead to further system compromise and privilege elevation within the network environment. Organizations should also consider implementing network access control lists and monitoring for anomalous DHCP response patterns to detect potential exploitation attempts before they can succeed.