CVE-2021-25659 in Automation License Manager
Summary
by MITRE • 08/10/2021
A vulnerability has been identified in Automation License Manager 5 (All versions), Automation License Manager 6 (All versions < V6.0 SP9 Update 2). Sending specially crafted packets to port 4410/tcp of an affected system could lead to extensive memory being consumed and as such could cause a denial-of-service preventing legitimate users from using the system.
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Analysis
by VulDB Data Team • 08/15/2021
The vulnerability CVE-2021-25659 represents a critical denial-of-service weakness in Siemens Automation License Manager software versions 5 and 6, specifically affecting systems prior to V6.0 SP9 Update 2. This flaw resides within the network communication handling mechanisms of the license management system, which operates on TCP port 4410. The vulnerability stems from insufficient input validation and memory management practices when processing incoming network packets, creating a condition where maliciously crafted data can trigger excessive memory consumption. The affected systems are particularly vulnerable during license validation and management operations, as these processes typically involve parsing and processing network requests from authorized clients and license servers. The flaw demonstrates characteristics consistent with CWE-400, which addresses unchecked resource consumption, and aligns with ATT&CK technique T1499.004 for network denial-of-service attacks. When exploited, the vulnerability allows an attacker to send specially crafted packets that cause the Automation License Manager service to allocate excessive memory resources without proper cleanup or bounds checking, leading to system instability and complete service unavailability.
The technical exploitation of this vulnerability involves sending malformed network packets to the designated TCP port 4410, which serves as the primary communication channel for license management operations within Siemens automation environments. The flaw occurs during the parsing of incoming protocol messages, where the software fails to properly validate packet structures and memory allocation requests. This lack of proper input sanitization creates a condition where memory exhaustion can occur rapidly through repeated or sustained exploitation attempts. The vulnerability is particularly concerning because it affects the core license management infrastructure that many industrial automation systems depend upon for proper operation and security validation. Network-based attacks can originate from any location that can reach the target system, making this vulnerability accessible to both external and internal threat actors. The memory consumption pattern suggests that the system may not properly release allocated memory segments or implement adequate resource limits during packet processing, creating a persistent resource leak that can eventually exhaust all available system memory.
The operational impact of CVE-2021-25659 extends beyond simple service disruption to potentially compromise entire industrial control systems that rely on proper license management for operational security. Organizations using affected Automation License Manager versions may experience complete system unavailability during license validation processes, affecting production workflows and maintenance operations. The vulnerability's presence in automation environments increases risk to critical infrastructure, as license management systems often serve as gateways for system access and operational authorization. When legitimate users cannot access license validation services, it can cascade into broader operational disruptions, affecting production scheduling, system updates, and security compliance verification. The vulnerability's impact is amplified in environments where multiple systems depend on centralized license management, creating potential for widespread service degradation across automation networks. Additionally, the resource exhaustion can cause system crashes that may require manual intervention and system restarts, leading to unplanned downtime and operational delays. The vulnerability also creates opportunities for attackers to leverage the service disruption for additional attacks, potentially using the denial-of-service as a precursor to more sophisticated exploitation attempts.
Mitigation strategies for CVE-2021-25659 should focus on both immediate defensive measures and long-term architectural improvements to protect automation license management systems. Organizations should immediately apply the vendor-provided patches and updates, specifically targeting V6.0 SP9 Update 2 or later versions for affected Automation License Manager 6 installations. Network-level protections should include implementing firewall rules that restrict access to TCP port 4410 to only authorized systems and IP addresses, effectively limiting the attack surface. Additional defensive measures involve configuring intrusion detection systems to monitor for unusual patterns of traffic to port 4410 and implementing rate limiting or connection throttling mechanisms to prevent rapid memory exhaustion attacks. System administrators should also establish monitoring protocols to detect memory usage spikes and automated alerting when system resources approach critical thresholds. The implementation of network segmentation strategies can help isolate license management services from general automation networks, reducing the potential impact of exploitation. Organizations should conduct regular vulnerability assessments and penetration testing to identify similar weaknesses in their industrial control system environments, ensuring comprehensive protection against related vulnerabilities. Security teams should also implement proper logging and audit controls to track license management activities and detect anomalous behavior that may indicate exploitation attempts.