CVE-2025-29971: Windows 11 22H2 DoS Vulnerability

CVE-2025-29971 Overview

CVE-2025-29971 is an out-of-bounds read vulnerability in the Web Threat Defense (WTD.sys) kernel driver component of Microsoft Windows 11. This vulnerability allows an unauthorized attacker to cause a denial of service condition over the network without requiring any authentication or user interaction.

Critical Impact

Remote attackers can exploit this vulnerability to cause system unavailability by triggering an out-of-bounds read condition in the WTD.sys driver, potentially resulting in system crashes or unresponsive services.

Affected Products

• Microsoft Windows 11 22H2 (x64 and ARM64)
• Microsoft Windows 11 23H2 (x64 and ARM64)
• Microsoft Windows 11 24H2 (x64 and ARM64)

Discovery Timeline

• May 13, 2025 - CVE-2025-29971 published to NVD
• May 19, 2025 - Last updated in NVD database

Technical Details for CVE-2025-29971

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-bounds Read), a memory corruption flaw that occurs when the Web Threat Defense driver reads data from a memory location outside the intended buffer boundaries. The WTD.sys driver is a kernel-mode component responsible for providing web threat defense capabilities in Windows 11.

When the driver processes specially crafted network traffic, it fails to properly validate buffer boundaries before performing read operations. This allows an attacker to trigger memory reads beyond the allocated buffer, which can cause the driver to access invalid memory regions. In a kernel-mode context, such out-of-bounds reads typically result in a system crash (Blue Screen of Death) as the kernel cannot gracefully handle invalid memory access.

The vulnerability requires no authentication and no user interaction, making it particularly concerning for internet-facing Windows 11 systems. An attacker can remotely trigger this condition by sending malicious network packets to a vulnerable system.

Root Cause

The root cause of CVE-2025-29971 lies in insufficient boundary validation within the WTD.sys driver when processing network data. The driver fails to properly verify that read operations remain within the bounds of allocated memory buffers before accessing data. This boundary checking deficiency allows attackers to induce memory reads from locations outside the intended buffer, leading to system instability.

Attack Vector

The attack vector for this vulnerability is network-based. An unauthorized remote attacker can exploit this flaw by sending specially crafted network packets to a target system running a vulnerable version of Windows 11. The attack does not require any privileges on the target system, nor does it require any action from users. The attacker simply needs network connectivity to the target system to trigger the out-of-bounds read condition in the WTD.sys driver.

The vulnerability mechanism involves malformed network traffic that causes the Web Threat Defense driver to perform memory read operations beyond allocated buffer boundaries. Technical implementation details are available in the Microsoft Security Advisory.

Detection Methods for CVE-2025-29971

Indicators of Compromise

• Unexpected system crashes or Blue Screen of Death (BSOD) events with WTD.sys referenced in crash dumps
• Unusual network traffic patterns targeting web threat defense services
• Kernel crash logs indicating memory access violations in kernel drivers
• Event log entries showing driver faults or unexpected service terminations

Detection Strategies

• Monitor Windows Event Logs for kernel driver crashes, specifically filtering for WTD.sys related events
• Deploy network intrusion detection systems (NIDS) to identify anomalous traffic patterns that may indicate exploitation attempts
• Configure endpoint detection and response (EDR) solutions to alert on kernel-mode exceptions and driver faults
• Analyze crash dumps for evidence of out-of-bounds memory access patterns

Monitoring Recommendations

• Enable verbose logging for kernel driver events and system crashes
• Implement centralized log collection to correlate BSOD events across the enterprise
• Configure SentinelOne Singularity Platform to monitor for kernel-level anomalies and driver stability issues
• Establish baseline network traffic patterns to identify deviations that may indicate exploitation attempts

How to Mitigate CVE-2025-29971

Immediate Actions Required

• Apply the latest Microsoft security updates for Windows 11 immediately
• Prioritize patching for internet-facing and business-critical systems
• Review network segmentation to limit exposure of vulnerable systems
• Monitor for indicators of compromise on systems pending updates

Patch Information

Microsoft has released security updates to address this vulnerability. Administrators should consult the Microsoft Security Advisory for CVE-2025-29971 for detailed patch information and download links specific to their Windows 11 version. Apply the appropriate cumulative update through Windows Update, WSUS, or manual deployment methods.

Workarounds

• Implement network-level filtering to restrict access to affected services where possible
• Consider enabling additional network monitoring at perimeter firewalls to detect potential exploitation attempts
• Deploy defense-in-depth strategies including network segmentation to isolate vulnerable systems
• Utilize SentinelOne's Singularity Platform for real-time threat detection and response capabilities

# Check current Windows 11 build version
winver

# Verify WTD.sys driver version via PowerShell
Get-Item C:\Windows\System32\drivers\WTD.sys | Select-Object -ExpandProperty VersionInfo

# Force Windows Update check
usoclient StartScan