CVE-2026-50370 Overview
CVE-2026-50370 is a heap-based buffer overflow vulnerability in the Microsoft Windows Dynamic Host Configuration Protocol (DHCP) Server service. An unauthenticated attacker on an adjacent network can trigger the flaw to execute arbitrary code in the context of the DHCP service. Because DHCP servers typically run with elevated privileges, successful exploitation can lead to full system compromise and lateral movement across affected subnets. The vulnerability is tracked under [CWE-20] Improper Input Validation and affects multiple supported Windows Server and Windows 10 builds.
Critical Impact
Unauthenticated adjacent-network attackers can achieve remote code execution on Windows DHCP Servers, compromising confidentiality, integrity, and availability of core network infrastructure.
Affected Products
- Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025
- Microsoft Windows 10 version 1607 (x86 and x64)
- Microsoft Windows 10 version 1809 (x86 and x64)
Discovery Timeline
- 2026-07-14 - CVE-2026-50370 published to the National Vulnerability Database (NVD)
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-50370
Vulnerability Analysis
The flaw resides in the Windows DHCP Server service, which handles DHCP request and discover messages from clients on the local network segment. Improper validation of attacker-controlled fields within a DHCP message causes the service to write beyond an allocated heap buffer. An attacker who crafts a malicious DHCP packet can corrupt adjacent heap metadata or function pointers, redirecting execution flow.
Exploitation does not require authentication or user interaction. The attack is limited to an adjacent network because DHCP traffic is typically not routed beyond the local broadcast domain. Successful exploitation yields code execution in the DHCP service context, which normally runs with SYSTEM-level privileges on Windows Server.
Root Cause
The underlying weakness is [CWE-20] Improper Input Validation. The DHCP Server service fails to properly bound-check attacker-supplied option data before copying it into a heap-allocated buffer. This missing validation permits a classic heap overflow condition, enabling memory corruption primitives usable for arbitrary code execution.
Attack Vector
An attacker positioned on the same broadcast domain as a vulnerable Windows DHCP Server sends a specially crafted DHCP message. The malformed message triggers the overflow during option parsing. No credentials, prior access, or user interaction are required. Rogue devices connected to guest networks, compromised IoT endpoints, or attacker-controlled virtual machines within a hypervisor segment all represent realistic launch points.
No public proof-of-concept exploit or exploitation in the wild has been reported at the time of publication. Refer to the Microsoft Security Response Center advisory for CVE-2026-50370 for technical details.
Detection Methods for CVE-2026-50370
Indicators of Compromise
- Unexpected crashes or restarts of the DHCPServer service (Event IDs 7031, 7034) on domain controllers or dedicated DHCP hosts.
- Anomalous DHCP DISCOVER or REQUEST packets containing oversized or malformed option fields captured on the local subnet.
- New or unrecognized child processes spawned from svchost.exe hosting the DHCP Server service.
Detection Strategies
- Monitor Windows Event Log channels Microsoft-Windows-DHCP-Server/Operational and System for service crashes correlating with inbound DHCP traffic bursts.
- Deploy network intrusion detection signatures that inspect DHCP option lengths and flag packets exceeding expected boundaries.
- Correlate memory-access violations in dhcpssvc.dll with process telemetry to identify exploitation attempts against the service.
Monitoring Recommendations
- Baseline normal DHCP traffic volume and alert on sudden spikes or malformed packet ratios from single MAC addresses.
- Enable enhanced auditing on servers running the DHCP role and forward logs to a centralized SIEM for retention and correlation.
- Track lateral movement indicators originating from DHCP servers, including unexpected SMB or WMI connections following service anomalies.
How to Mitigate CVE-2026-50370
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50370 to all affected Windows Server and Windows 10 systems running the DHCP Server role.
- Inventory all systems with the DHCP Server role enabled and prioritize patching for internet-adjacent and multi-tenant network segments.
- Segment DHCP servers onto trusted management VLANs to reduce exposure to untrusted adjacent hosts.
Patch Information
Microsoft has issued security updates addressing CVE-2026-50370 for all affected Windows versions listed in the advisory. Administrators should deploy the corresponding cumulative update through Windows Update, Windows Server Update Services (WSUS), or Microsoft Update Catalog. Verify patch installation using Get-HotFix or the update history in Settings.
Workarounds
- Disable the DHCP Server service on hosts where the role is not required using Stop-Service DHCPServer and Set-Service DHCPServer -StartupType Disabled.
- Enforce DHCP snooping on managed switches to drop DHCP traffic from untrusted ports and limit exposure of the server to rogue clients.
- Restrict physical and logical access to network segments hosting DHCP servers, isolating guest, IoT, and BYOD networks from server VLANs.
# Disable DHCP Server service on hosts where the role is not needed
Stop-Service -Name DHCPServer -Force
Set-Service -Name DHCPServer -StartupType Disabled
# Verify patch installation (replace KB number with the applicable update)
Get-HotFix | Where-Object { $_.HotFixID -like 'KB*' } | Sort-Object InstalledOn -Descending
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
