CVE-2013-5537 in Content Security Management Appliance
Summary
by MITRE
The web framework on Cisco Web Security Appliance (WSA), Email Security Appliance (ESA), and Content Security Management Appliance (SMA) devices does not properly manage the state of HTTP and HTTPS sessions, which allows remote attackers to cause a denial of service (management GUI outage) via multiple TCP connections, aka Bug IDs CSCuj59411, CSCuf89818, and CSCuh05635.
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Analysis
by VulDB Data Team • 03/25/2019
The vulnerability identified as CVE-2013-5537 affects Cisco's security appliances including the Web Security Appliance WSA, Email Security Appliance ESA, and Content Security Management Appliance SMA. This issue stems from improper session state management within the web framework component of these devices, creating a significant weakness that can be exploited remotely. The flaw specifically targets the handling of HTTP and HTTPS session states, which are critical for maintaining secure and stable communication between administrative interfaces and users. The vulnerability represents a fundamental failure in session management protocols that govern how these appliances maintain and track user sessions through TCP connections.
The technical implementation of this vulnerability allows remote attackers to exploit the insufficient session state handling by establishing multiple TCP connections to the affected appliances. When these connections are made in a specific manner, the appliances fail to properly manage the state transitions and connection handling, leading to a cascading failure in the management GUI service. This mismanagement results in the complete outage of the administrative interface, effectively rendering the device inaccessible for management purposes. The vulnerability operates at the application layer of the network stack, specifically targeting the web framework's session handling mechanisms that are responsible for maintaining connection state information. The flaw is classified under CWE-362, which addresses "Concurrent Execution using Shared Resource with Improper Synchronization," indicating that the session management lacks proper synchronization controls to handle concurrent connections.
The operational impact of this vulnerability is severe and directly affects the availability of critical security infrastructure. When the management GUI becomes unavailable due to this denial of service condition, administrators lose the ability to monitor, configure, or troubleshoot the security appliances remotely. This creates a significant operational risk as security policies cannot be updated or adjusted during an attack, and the appliances become effectively non-functional from a management perspective. The vulnerability can be exploited without requiring authentication, making it particularly dangerous as any remote attacker can trigger the condition. The attack vector leverages the inherent design flaw in how TCP connections are managed during session establishment and maintenance, allowing an attacker to consume system resources or trigger state machine failures that ultimately result in service disruption.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004, which involves network denial of service attacks targeting management interfaces. The exploitation pattern demonstrates how weaknesses in session management can be leveraged to achieve availability compromise, a critical aspect of the CIA triad. Organizations using these Cisco appliances face significant risk as the vulnerability can be triggered through simple network-based attacks that do not require advanced exploitation techniques or privileged access. The flaw essentially creates a race condition or resource exhaustion scenario where multiple concurrent connections overwhelm the session handling mechanisms. Mitigation strategies should include implementing connection rate limiting, monitoring for unusual connection patterns, and applying Cisco's official security patches as soon as they become available. Network segmentation and access control measures can help reduce the attack surface, though the most effective solution involves proper firmware updates that address the underlying session management implementation flaws.
The broader implications of this vulnerability extend beyond immediate service disruption to highlight the importance of robust session management in security appliances. Many organizations rely heavily on centralized management interfaces for their security infrastructure, making such vulnerabilities particularly dangerous as they can disable entire security ecosystems simultaneously. The vulnerability also demonstrates how seemingly minor implementation flaws in web frameworks can have significant operational consequences when they affect core administrative functions. This issue serves as a reminder of the critical need for thorough security testing of management interfaces and the importance of proper synchronization mechanisms in concurrent systems. Organizations should implement monitoring solutions that can detect unusual connection patterns or resource consumption spikes that might indicate exploitation attempts, while also maintaining regular patching schedules to address known vulnerabilities in their security infrastructure components.