CVE-2019-0785 in Windows
Summary
by MITRE
A memory corruption vulnerability exists in the Windows Server DHCP service when an attacker sends specially crafted packets to a DHCP failover server, aka 'Windows DHCP Server Remote Code Execution Vulnerability'.
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Analysis
by VulDB Data Team • 07/09/2020
The vulnerability identified as CVE-2019-0785 represents a critical memory corruption flaw within the Windows Server Dynamic Host Configuration Protocol service that specifically affects DHCP failover server implementations. This vulnerability stems from improper handling of specially crafted network packets that can be transmitted to DHCP failover servers, creating a remote code execution vector that adversaries can exploit without requiring authentication credentials. The flaw exists in the processing logic of the DHCP server's failover mechanism, where insufficient input validation allows maliciously constructed packets to trigger memory corruption conditions that can be leveraged for arbitrary code execution.
The technical nature of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which encompasses out-of-bounds read vulnerabilities that can lead to memory corruption. The flaw manifests when the DHCP server processes failover messages containing malformed data structures that exceed allocated memory boundaries or corrupt existing memory segments. Attackers can exploit this by sending specifically crafted DHCP failover packets that cause the server process to write beyond allocated memory regions, potentially leading to stack corruption, heap corruption, or other memory management issues that can be manipulated to execute malicious code with the privileges of the affected service account.
From an operational perspective, this vulnerability poses significant risk to enterprise networks that rely on Windows Server DHCP failover configurations, which are commonly implemented to ensure high availability and redundancy in network infrastructure. The remote code execution capability means that attackers can potentially compromise entire network segments without physical access or valid credentials, as the vulnerability can be exploited from any network location where the attacker can reach the DHCP server. This makes it particularly dangerous in environments where DHCP servers are exposed to untrusted networks or where proper network segmentation has not been implemented. The vulnerability affects Windows Server 2012 R2, Windows Server 2016, and Windows Server 2019 versions that have DHCP failover functionality enabled.
The exploitation of CVE-2019-0785 can be mapped to multiple ATT&CK tactics including TA0002 (Execution) and TA0005 (Defense Evasion), as attackers can leverage this vulnerability to execute malicious code and potentially establish persistence mechanisms. The vulnerability also supports TA0006 (Credential Access) and TA0008 (Lateral Movement) tactics when successful exploitation leads to privilege escalation or allows attackers to move laterally within the network. Security professionals should note that the vulnerability's impact is amplified when DHCP failover servers are configured in active-passive or active-active modes, as these configurations increase the attack surface and provide multiple potential entry points for exploitation.
Mitigation strategies for CVE-2019-0785 should include immediate deployment of Microsoft security updates that address the memory corruption issues in the DHCP server implementation. Organizations should also implement network segmentation to limit access to DHCP servers, particularly ensuring that only authorized network segments can communicate with these critical infrastructure components. Additional defensive measures include monitoring for unusual DHCP traffic patterns, implementing network access controls to restrict which systems can send DHCP messages to failover servers, and establishing robust network monitoring to detect potential exploitation attempts. The vulnerability also underscores the importance of maintaining up-to-date security patches and implementing proper network architecture principles that reduce the attack surface of critical services. Organizations should consider implementing intrusion detection systems that can identify and alert on suspicious DHCP traffic patterns that may indicate exploitation attempts, and should conduct regular security assessments to identify and remediate similar vulnerabilities in other network infrastructure components.