CVE-2026-27925: Windows UPnP Use-After-Free Vulnerability

CVE-2026-27925 Overview

A use-after-free vulnerability exists in the Windows Universal Plug and Play (UPnP) Device Host service that allows an unauthorized attacker to disclose sensitive information over an adjacent network. This memory corruption flaw occurs when the UPnP service improperly handles memory after it has been freed, potentially exposing confidential data to attackers on the same network segment.

Critical Impact

Successful exploitation of this vulnerability enables attackers with adjacent network access to extract sensitive information from affected Windows systems without requiring authentication or user interaction.

Affected Products

• Windows Universal Plug and Play (UPnP) Device Host
• Windows systems with UPnP services enabled
• Network-attached Windows devices running vulnerable UPnP implementations

Discovery Timeline

• April 14, 2026 - CVE-2026-27925 published to NVD
• April 14, 2026 - Last updated in NVD database

Technical Details for CVE-2026-27925

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption vulnerability where the application continues to reference memory after it has been deallocated. In the context of the Windows UPnP Device Host service, this flaw allows attackers positioned on an adjacent network to trigger the condition and read sensitive data from the freed memory regions.

The adjacent network attack vector indicates that exploitation requires the attacker to be on the same local network segment as the target system—such as the same LAN, Wi-Fi network, or VLAN. This limits the attack surface compared to remote network attacks but remains a significant concern for enterprise environments and shared network infrastructure.

The vulnerability can be exploited without any privileges or user interaction, making it particularly concerning for environments where UPnP services are exposed on internal networks. The primary impact is information disclosure with high confidentiality impact, though integrity and availability are not affected.

Root Cause

The root cause is a use-after-free condition in the Windows UPnP Device Host service. This occurs when the service frees a memory object but fails to properly invalidate all references to that memory. When the service subsequently accesses this freed memory through a dangling pointer, it can read arbitrary data that may have been reallocated for other purposes, leading to information disclosure.

Attack Vector

The attack requires adjacent network access to the target system running the vulnerable Windows UPnP Device Host service. An attacker can craft malicious UPnP requests or responses that trigger the use-after-free condition. When the vulnerable code path is executed:

1. A memory object is allocated and used by the UPnP service
2. The object is freed but pointers to it are not properly nullified
3. Attacker-controlled input triggers access to the freed memory
4. Sensitive data present in the reallocated memory region is disclosed to the attacker

The attack does not require authentication or user interaction, making automated exploitation feasible for attackers with network adjacency.

Detection Methods for CVE-2026-27925

Indicators of Compromise

• Unusual UPnP traffic patterns from unexpected sources on the local network
• Anomalous memory access patterns or crashes in the upnphost service
• Unexpected outbound data exfiltration following UPnP service activity
• Process memory anomalies or heap corruption signatures associated with svchost.exe hosting UPnP services

Detection Strategies

• Monitor for abnormal UPnP protocol traffic on ports 1900/UDP and 2869/TCP from unauthorized or suspicious endpoints
• Deploy endpoint detection and response (EDR) solutions to detect memory corruption exploitation attempts targeting the UPnP Device Host service
• Implement network segmentation monitoring to identify lateral movement attempts leveraging UPnP vulnerabilities
• Use Windows Event Logs to correlate UPnP service crashes or restarts with potential exploitation activity

Monitoring Recommendations

• Enable advanced auditing for the Windows UPnP Device Host service and monitor for service instability
• Implement network traffic analysis to baseline normal UPnP behavior and alert on deviations
• Monitor for process memory anomalies in services hosting UPnP functionality using behavioral analysis tools
• Review network access logs for unauthorized devices attempting UPnP discovery or communication

How to Mitigate CVE-2026-27925

Immediate Actions Required

• Apply the latest Microsoft security updates as soon as they become available
• Disable the UPnP Device Host service (upnphost) on systems where it is not required
• Implement network segmentation to limit adjacent network attack surfaces
• Enable host-based firewall rules to restrict UPnP traffic to trusted sources only

Patch Information

Microsoft has released a security update to address this vulnerability. Detailed patch information is available in the Microsoft Security Update Guide for CVE-2026-27925. Organizations should prioritize deploying this update to all affected Windows systems, particularly those in environments with shared network infrastructure.

Workarounds

• Disable the Windows UPnP Device Host service via Services console (services.msc) or Group Policy if UPnP functionality is not required
• Configure Windows Firewall to block inbound UPnP traffic on ports 1900/UDP and 2869/TCP from untrusted network segments
• Implement network access control (NAC) to restrict which devices can communicate via UPnP protocols
• Deploy micro-segmentation to isolate systems running UPnP services from general network traffic

# Disable UPnP Device Host service via PowerShell
Stop-Service -Name "upnphost" -Force
Set-Service -Name "upnphost" -StartupType Disabled

# Block UPnP traffic via Windows Firewall
netsh advfirewall firewall add rule name="Block UPnP Discovery" dir=in action=block protocol=udp localport=1900
netsh advfirewall firewall add rule name="Block UPnP HTTP" dir=in action=block protocol=tcp localport=2869