CVE-2025-27469 in Windows
Summary
by MITRE • 04/08/2025
Uncontrolled resource consumption in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 05/26/2026
This vulnerability represents a critical denial of service weakness in the Windows Lightweight Directory Access Protocol implementation that can be exploited by unauthorized attackers to consume excessive system resources. The flaw manifests when the LDAP service fails to properly validate or limit resource consumption during directory queries and authentication operations, allowing malicious actors to craft specially crafted requests that trigger unbounded resource allocation. This issue falls under the broader category of resource exhaustion attacks that target network services and can result in complete service unavailability for legitimate users. The vulnerability is particularly dangerous because it can be exploited remotely without requiring authentication, making it an attractive target for attackers seeking to disrupt directory services within enterprise environments. According to the CWE database, this represents a variant of CWE-400 Uncontrolled Resource Consumption which encompasses various resource exhaustion scenarios including memory, CPU, and file descriptor exhaustion. The attack vector typically involves sending malformed or excessively complex LDAP queries that cause the server to allocate increasing amounts of memory or processing power without proper bounds checking. Organizations relying on Active Directory services and LDAP for authentication and directory lookups face significant operational risks when this vulnerability remains unpatched, as it can affect critical business processes that depend on directory service availability. The impact extends beyond simple service disruption to potentially affect authentication systems, group policy applications, and other directory-dependent services that form the foundation of enterprise network security infrastructure.
The technical exploitation of this vulnerability leverages the inherent design characteristics of LDAP protocol implementations in Windows environments where resource limits are not properly enforced during query processing. Attackers can construct LDAP search filters or bind operations that cause the server to perform excessive work or allocate memory in a way that grows without bounds, leading to system instability or complete resource exhaustion. This behavior aligns with ATT&CK technique T1499.004 Network Denial of Service which specifically targets network services through resource exhaustion attacks. The vulnerability often manifests when processing complex nested search filters, large attribute sets, or recursive queries that trigger inefficient processing paths within the LDAP server implementation. Windows LDAP service typically operates on standard ports 389 for unencrypted connections and 636 for SSL/TLS encrypted connections, making it accessible to attackers from both internal and external network positions. The resource consumption patterns vary based on the specific LDAP operations performed but commonly include memory allocation spikes, thread exhaustion, or CPU utilization that can quickly overwhelm system resources. Security researchers have identified that this vulnerability is particularly prevalent in older Windows versions and may be present in various Microsoft server products including Windows Server 2008, 2012, 2016, and 2019 versions. The exploitation requires minimal privileges and can be automated through simple scripts that repeatedly submit resource-intensive LDAP queries until system resources are depleted. Organizations should note that this vulnerability affects not just standalone LDAP servers but also domain controllers and other Windows systems that implement LDAP services as part of their directory infrastructure. The operational impact includes extended downtime for directory services, potential cascading failures affecting dependent systems, and disruption of authentication processes that can affect user productivity and system access. Additionally, the vulnerability may be exploited as part of broader attack campaigns where attackers first establish resource exhaustion to disable security monitoring systems before launching more sophisticated attacks against the same infrastructure.
Mitigation strategies for this vulnerability must address both immediate protection and long-term architectural improvements to prevent resource exhaustion attacks against LDAP services. The most effective immediate solution involves applying the relevant Microsoft security updates that address the specific resource consumption flaws in LDAP implementations. Organizations should also implement network-level protections such as rate limiting, connection throttling, and access control lists that restrict LDAP query complexity and frequency. Implementing LDAP query monitoring and alerting systems can help detect anomalous resource consumption patterns before they lead to complete service disruption. Network segmentation and firewall rules should be configured to limit access to LDAP ports to only trusted sources and applications that require directory access. The implementation of proper LDAP service hardening measures including setting appropriate memory limits, connection timeouts, and query result size limits can significantly reduce the attack surface. Security teams should also consider implementing intrusion detection systems that can identify and block suspicious LDAP traffic patterns that match known exploitation signatures. Regular security assessments and penetration testing should include LDAP service testing to identify potential resource consumption vulnerabilities that may not be covered by standard patches. Organizations should maintain detailed logging of LDAP operations and establish baseline performance metrics to quickly identify when resource consumption patterns deviate from normal operations. The deployment of redundant LDAP services and proper load balancing configurations can help distribute the risk and provide failover capabilities when individual LDAP servers become compromised by resource exhaustion attacks. Additionally, implementing proper incident response procedures that include LDAP service recovery and restoration protocols ensures minimal downtime when vulnerabilities are successfully exploited. Organizations should also consider migrating to more modern authentication and directory services that have better resource management and protection mechanisms against such attacks.