CVE-2015-2535 in Windows
Summary
by MITRE
Active Directory in Microsoft Windows Server 2008 SP2 and R2 SP1 and Server 2012 Gold and R2 allows remote authenticated users to cause a denial of service (service outage) by creating multiple machine accounts, aka "Active Directory Denial of Service Vulnerability."
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Analysis
by VulDB Data Team • 06/14/2022
The vulnerability identified as CVE-2015-2535 represents a critical denial of service weakness within Microsoft Active Directory services running on Windows Server 2008 SP2, R2 SP1, and Server 2012 Gold and R2 versions. This flaw operates at the directory service level where Active Directory maintains the authoritative database of network resources and user permissions. The vulnerability stems from insufficient validation mechanisms within the Active Directory service that governs machine account creation processes. When an authenticated attacker exploits this weakness, they can systematically generate multiple machine accounts within the domain, ultimately exhausting available resources and causing the directory service to become unresponsive.
The technical implementation of this vulnerability involves the exploitation of the Active Directory replication and account creation protocols. Specifically, the flaw exists in how the system handles concurrent machine account creation requests without proper rate limiting or resource allocation controls. Machine accounts in Active Directory serve as security principals that represent computers joined to the domain, and their creation typically involves complex synchronization processes across domain controllers. The vulnerability allows an attacker to bypass normal account creation limits and create accounts in rapid succession, leading to resource exhaustion at the domain controller level. This issue maps directly to CWE-400, which categorizes "Uncontrolled Resource Consumption" as a fundamental weakness in software design that enables denial of service attacks through resource depletion.
From an operational perspective, this vulnerability presents a significant risk to enterprise network stability and business continuity. The denial of service condition affects the core authentication and authorization infrastructure that thousands of network resources depend upon. Domain controllers experiencing this vulnerability become unable to process legitimate authentication requests, effectively cutting off access to network resources for all domain-joined machines and users. The impact extends beyond simple service interruption as it can cascade through the entire network infrastructure, affecting file servers, database systems, and application servers that rely on Active Directory for user authentication and group policy enforcement. Network administrators may experience extended downtime while investigating and resolving the service outage, particularly since the attack can be executed remotely with valid credentials, making detection and attribution more challenging.
The attack vector for CVE-2015-2535 requires only authenticated access to the domain, meaning that any user with valid domain credentials can potentially exploit this vulnerability. This characteristic makes the attack surface particularly broad as it can be initiated by compromised accounts, insider threats, or attackers who have obtained legitimate credentials through various means including credential theft, phishing, or brute force attacks. The vulnerability aligns with several ATT&CK techniques including T1078 for valid accounts and T1499 for network denial of service, demonstrating how this weakness can be leveraged as part of broader attack campaigns. Organizations should consider implementing network segmentation and access controls to limit the scope of potential exploitation, as well as monitoring for unusual machine account creation patterns that may indicate an active attack.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both immediate defensive measures and long-term architectural improvements. Microsoft released security updates and patches addressing this specific weakness, and organizations should prioritize deployment of these updates across all affected server versions. Additional defensive measures include implementing account lockout policies, monitoring Active Directory for abnormal account creation patterns, and configuring domain controller resource limits to prevent complete service exhaustion. Network administrators should also consider implementing additional authentication controls such as Kerberos pre-authentication requirements and monitoring for suspicious authentication patterns that could indicate exploitation attempts. The remediation process should include comprehensive testing of patches in non-production environments to ensure compatibility with existing network infrastructure and business applications.