CVE-2019-1206 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. An attacker who successfully exploited the vulnerability could cause the DHCP service to become nonresponsive. To exploit the vulnerability, an attacker could send a specially crafted packet to a DHCP server. However, the DHCP server must be set to failover mode for the attack to succeed. The security update addresses the vulnerability by correcting how DHCP failover servers handle network packets.
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Analysis
by VulDB Data Team • 02/21/2026
The vulnerability identified as CVE-2019-1206 represents a critical memory corruption flaw within the Windows Server Dynamic Host Configuration Protocol DHCP service that specifically manifests when the DHCP server operates in failover mode. This weakness stems from inadequate input validation and memory management within the DHCP failover implementation, creating a potential avenue for denial of service attacks that could severely disrupt network infrastructure operations. The vulnerability is particularly concerning because it requires minimal network access to exploit, making it accessible to attackers with basic network connectivity to the target server.
The technical exploitation of CVE-2019-1206 occurs through the deliberate crafting of malicious network packets that target the DHCP failover server's packet processing routines. When the vulnerable DHCP server receives these specially constructed packets, the memory corruption causes the service to become unresponsive or crash entirely, effectively denying legitimate network clients the ability to obtain IP addresses and other network configuration parameters. This memory corruption issue falls under CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write vulnerabilities, both of which are common attack vectors in network service implementations. The attack pattern aligns with techniques documented in the ATT&CK framework under T1499.004 for network denial of service attacks, where adversaries target critical infrastructure services to disrupt operations.
The operational impact of this vulnerability extends beyond simple service disruption, as DHCP failover servers typically serve as critical components in enterprise network infrastructure, providing redundancy and availability for IP address allocation services. When such servers become unresponsive, network operations can experience significant downtime, potentially affecting thousands of devices that rely on dynamic IP address assignment. Organizations with mission-critical network dependencies may face substantial business disruption, as the failure of DHCP services can cascade through entire network segments, affecting authentication systems, application connectivity, and user access to network resources. The vulnerability's requirement for failover mode configuration means that organizations with properly configured DHCP servers in standard mode remain unaffected, but those implementing redundant DHCP infrastructure face heightened risk.
Mitigation strategies for CVE-2019-1206 should prioritize immediate implementation of the security update provided by Microsoft, which addresses the memory handling issues in DHCP failover packet processing. Network administrators should also implement additional protective measures including network segmentation to isolate DHCP servers, monitoring for anomalous packet patterns, and implementing access controls to limit which systems can communicate with DHCP failover servers. The security update specifically addresses the root cause by correcting how DHCP failover servers process incoming network packets, preventing the memory corruption that leads to service unresponsiveness. Organizations should conduct comprehensive vulnerability assessments to identify all DHCP servers operating in failover mode and ensure proper patching schedules are maintained to prevent similar vulnerabilities from being exploited in the future, aligning with best practices outlined in the NIST Cybersecurity Framework for critical infrastructure protection.