CVE-2025-27469: Windows 10 1507 LDAP DoS Vulnerability

CVE-2025-27469 Overview

CVE-2025-27469 is an uncontrolled resource consumption vulnerability in the Windows Lightweight Directory Access Protocol (LDAP) service that enables unauthorized attackers to cause a denial of service condition over a network. This vulnerability affects the LDAP implementation across a broad range of Microsoft Windows client and server operating systems, posing significant risk to enterprise environments that rely on Active Directory infrastructure.

The vulnerability stems from improper handling of resource consumption (CWE-400) within the Windows LDAP service, allowing remote unauthenticated attackers to exhaust system resources and render LDAP services unavailable. Given that LDAP is a critical component of Active Directory authentication and directory services, successful exploitation could disrupt authentication, group policy processing, and other essential enterprise operations.

Critical Impact

Remote unauthenticated attackers can cause denial of service against Windows LDAP services, potentially disrupting Active Directory authentication and directory services across the enterprise.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
• Microsoft Windows 11 (versions 22H2, 23H2, 24H2)
• Microsoft Windows Server 2008 SP2 and R2 SP1
• Microsoft Windows Server 2012 and R2
• Microsoft Windows Server 2016
• Microsoft Windows Server 2019
• Microsoft Windows Server 2022 and 23H2
• Microsoft Windows Server 2025

Discovery Timeline

• April 8, 2025 - CVE-2025-27469 published to NVD
• July 8, 2025 - Last updated in NVD database

Technical Details for CVE-2025-27469

Vulnerability Analysis

This vulnerability represents an uncontrolled resource consumption flaw in the Windows LDAP service. The vulnerability allows attackers to send specially crafted requests that cause the LDAP service to consume excessive system resources without proper limits or throttling mechanisms in place.

The attack can be initiated remotely over the network without requiring any authentication or user interaction, making it particularly dangerous for internet-exposed or poorly segmented LDAP services. When exploited, the target system's LDAP service becomes overwhelmed, leading to service degradation or complete unavailability.

In enterprise environments, LDAP services are fundamental to Active Directory operations, including user authentication, authorization decisions, group policy retrieval, and directory queries. A successful denial of service attack against LDAP could cascade to affect numerous dependent services and applications.

Root Cause

The root cause of CVE-2025-27469 is classified as CWE-400 (Uncontrolled Resource Consumption). The Windows LDAP implementation fails to properly limit or regulate the consumption of system resources when processing certain requests. This allows an attacker to craft requests that force the service to allocate excessive memory, CPU cycles, or other finite resources, eventually exhausting available capacity and causing service disruption.

The vulnerability exists because the LDAP service does not implement adequate safeguards to prevent resource exhaustion attacks, such as connection rate limiting, request throttling, or maximum resource allocation caps per client session.

Attack Vector

The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely over a network connection. The attack characteristics include:

• Network-accessible: The attacker must be able to reach the LDAP service over the network (typically TCP port 389 for LDAP or TCP port 636 for LDAPS)
• No authentication required: The vulnerability can be exploited without valid credentials
• No user interaction: Exploitation does not require any action from users on the target system
• Availability impact: The primary consequence is denial of service affecting LDAP availability

An attacker would typically send a high volume of malformed or resource-intensive LDAP requests to the target server, causing the LDAP service to consume excessive resources. This could involve crafted search queries, bind requests, or other LDAP operations designed to maximize resource consumption on the server side.

Detection Methods for CVE-2025-27469

Indicators of Compromise

• Unusual spikes in LDAP service resource consumption (CPU, memory) on Domain Controllers
• High volume of LDAP connection attempts from single or multiple source IP addresses
• LDAP service crashes, restarts, or unresponsiveness affecting authentication operations
• Event log entries indicating LDAP service resource exhaustion or performance degradation

Detection Strategies

• Monitor Domain Controller performance counters for abnormal LDAP operation patterns and resource utilization
• Implement network-based detection rules to identify unusual LDAP traffic volumes or patterns
• Configure Windows Event Log monitoring for LDAP-related errors and warnings (Event IDs in the Directory Services log)
• Deploy behavioral analysis to detect deviation from baseline LDAP traffic patterns

Monitoring Recommendations

• Enable detailed LDAP logging on Domain Controllers to capture request patterns
• Set up alerting thresholds for LDAP service CPU and memory consumption
• Monitor network traffic on LDAP ports (389, 636) for volumetric anomalies
• Implement SIEM correlation rules to detect coordinated LDAP flooding attempts

How to Mitigate CVE-2025-27469

Immediate Actions Required

• Apply the Microsoft security update for CVE-2025-27469 as the primary remediation
• Review and restrict network access to LDAP services, limiting exposure to trusted networks only
• Ensure Domain Controllers are not directly exposed to untrusted networks or the internet
• Consider implementing LDAP connection rate limiting at the network firewall level

Patch Information

Microsoft has released security updates to address this vulnerability. Administrators should consult the Microsoft Security Update Guide for CVE-2025-27469 for specific patch information and download links for affected operating system versions.

The security update addresses the uncontrolled resource consumption issue by implementing proper resource management controls within the Windows LDAP service.

Workarounds

• Restrict LDAP service access to only authorized IP ranges using Windows Firewall or network firewalls
• Implement network segmentation to isolate Domain Controllers from untrusted network segments
• Configure LDAP signing and channel binding to reduce attack surface and enforce authenticated connections
• Monitor and rate-limit LDAP connections at the network perimeter if patching is not immediately possible

# Windows Firewall rule to restrict LDAP access to specific subnet
netsh advfirewall firewall add rule name="Restrict LDAP Access" dir=in action=allow protocol=tcp localport=389 remoteip=10.0.0.0/8
netsh advfirewall firewall add rule name="Block External LDAP" dir=in action=block protocol=tcp localport=389 remoteip=any