CVE-2009-2053 in Unified Communications Manager
Summary
by MITRE
Cisco Unified Communications Manager (aka CUCM, formerly CallManager) 4.x, 5.x before 5.1(3g), 6.x before 6.1(4), 7.0 before 7.0(2a)su1, and 7.1 before 7.1(2) allows remote attackers to cause a denial of service (file-descriptor exhaustion and SCCP outage) via a flood of TCP packets, aka Bug ID CSCsx32236.
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Analysis
by VulDB Data Team • 03/30/2025
Cisco Unified Communications Manager represents a critical component in enterprise voice communication infrastructure, serving as the central call control platform for voice and video communications. The vulnerability described in CVE-2009-2053 specifically targets the SCCP (Skinny Client Control Protocol) implementation within these versions of CUCM, which governs communication between the central server and IP phones. This flaw manifests as a denial of service condition that can be triggered remotely through TCP packet flooding attacks, effectively exhausting system file descriptors and causing complete SCCP service outages. The vulnerability affects multiple major release versions including 4.x, 5.x, 6.x, 7.0, and 7.1, indicating a widespread impact across the product lineage. The root cause stems from insufficient input validation and resource management within the TCP connection handling mechanism, where the system fails to properly limit or throttle incoming TCP connections, leading to resource exhaustion. This vulnerability directly maps to CWE-400, which addresses "Uncontrolled Resource Consumption" and aligns with ATT&CK technique T1499.004 for "Endpoint Denial of Service" within the context of network infrastructure. The attack vector requires only network access to the affected CUCM system, making it particularly dangerous as it can be exploited from external networks without requiring authentication or privileged access. The operational impact extends beyond simple service interruption, as SCCP protocol failures can cascade throughout the entire communication infrastructure, affecting voice quality, call establishment, and potentially disrupting business continuity for organizations relying on these systems. The specific bug ID CSCsx32236 identifies the internal tracking mechanism for this vulnerability within Cisco's development lifecycle. Organizations using affected CUCM versions face significant risk of operational disruption, as the file descriptor exhaustion prevents the system from accepting new connections while potentially leaving existing connections in limbo. The vulnerability's remote exploitability means that attackers can target these systems from anywhere on the internet, making it particularly attractive for malicious actors seeking to disrupt communications. Network segmentation alone may not provide adequate protection, as the vulnerability affects core protocol handling rather than application-level defenses. The affected versions represent a critical window of exposure, as each major version line contained this flaw, requiring organizations to upgrade to patched releases to achieve proper protection. This vulnerability demonstrates the importance of proper resource management in telephony systems and highlights how protocol-level flaws can result in complete service outages. The impact on enterprise communications infrastructure can be severe, particularly for organizations that depend on continuous voice services for business operations, emergency response, or customer service. Organizations should implement network-based mitigations such as rate limiting and access control lists to reduce exposure while planning for proper patch management. The vulnerability also underscores the necessity of maintaining up-to-date security patches for mission-critical infrastructure components, as the exploitation can occur without any authentication requirements. Cisco's response to this vulnerability included release of patches for the affected versions, requiring system administrators to perform careful upgrade planning to avoid service disruption during patch installation. The remediation process involves not only applying the security patches but also ensuring that network configurations properly isolate critical communication infrastructure from potential attack vectors. This vulnerability serves as a reminder of the critical security considerations in voice communication systems and the potential for denial of service attacks to impact essential business operations. The technical complexity of the issue lies in the interaction between TCP connection handling, resource allocation, and protocol state management within the CUCM environment, requiring careful analysis and testing during patch implementation. Organizations should consider implementing intrusion detection systems to monitor for anomalous TCP traffic patterns that might indicate exploitation attempts, as well as conducting regular security assessments of their telephony infrastructure to identify similar vulnerabilities. The long-term implications of this vulnerability extend to security architecture design, emphasizing the need for robust resource management and connection handling within critical communication systems. Proper configuration management and security monitoring practices become essential for maintaining service availability in the face of such protocol-level vulnerabilities.