CVE-2024-21356 in Windows
Summary
by MITRE • 02/13/2024
Windows Lightweight Directory Access Protocol (LDAP) Denial of Service Vulnerability
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Analysis
by VulDB Data Team • 07/06/2026
This vulnerability affects the Lightweight Directory Access Protocol implementation within Microsoft Windows operating systems, specifically targeting the directory services functionality that enables secure authentication and authorization mechanisms. The flaw resides in how Windows processes certain LDAP requests, creating a potential denial of service condition that can be exploited by remote attackers to disrupt directory services. According to CWE-400, this represents a resource exhaustion vulnerability where malicious LDAP queries can cause the target system to consume excessive computational resources or memory, ultimately leading to service unavailability. The vulnerability is particularly concerning as it operates at the protocol level and can affect critical infrastructure components that rely on Active Directory for authentication and access control.
The technical implementation flaw involves improper input validation within the LDAP processing pipeline where specific malformed or crafted LDAP filter structures can trigger infinite loops or excessive memory allocation patterns. When a vulnerable Windows system receives such malicious requests, the LDAP service becomes unstable and may crash or become unresponsive, preventing legitimate users from accessing directory services. This behavior aligns with ATT&CK technique T1499.004 which describes denial of service attacks targeting network services and infrastructure components. The vulnerability affects multiple Windows versions including server and workstation operating systems that have LDAP client and server components enabled, making it a widespread concern for enterprise environments relying on directory services.
The operational impact of this vulnerability extends beyond simple service disruption as it can compromise the availability of critical business applications that depend on Active Directory for user authentication and authorization. Organizations may experience cascading failures where dependent systems become inaccessible due to the directory service outage, potentially affecting thousands of users simultaneously. Network administrators might find it challenging to identify the source of the disruption since the attack appears as normal network traffic, making detection difficult without proper monitoring capabilities. The vulnerability can be exploited by attackers with minimal privileges and requires no authentication to trigger the denial of service condition, making it particularly dangerous in environments where network segmentation is insufficient.
Effective mitigation strategies include implementing immediate security patches from Microsoft to address the underlying LDAP processing flaw, configuring network access controls to restrict LDAP traffic to trusted sources only, and deploying monitoring solutions that can detect anomalous LDAP query patterns. Organizations should also consider disabling unnecessary LDAP services on systems that do not require them and implement rate limiting mechanisms to prevent resource exhaustion attacks. Network segmentation practices should be enhanced to isolate directory services from general network traffic, reducing the attack surface for potential exploitation. Additionally, regular vulnerability assessments and security audits should be conducted to identify and remediate similar weaknesses in other directory service implementations or related protocols that might present comparable risks to enterprise environments.