CVE-2009-2052 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(2), and 7.1 before 7.1(2); and Cisco Unified Presence 1.x, 6.x before 6.0(6), and 7.x before 7.0(4); allows remote attackers to cause a denial of service (TCP services outage) via a large number of TCP connections, related to "tracking of network connections," aka Bug IDs CSCsq22534 and CSCsw52371.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/02/2025
Cisco Unified Communications Manager versions 4.x through 7.1 and Cisco Unified Presence 1.x through 7.0 contain a critical vulnerability in their TCP connection handling mechanisms that enables remote attackers to execute denial of service attacks. This vulnerability stems from inadequate tracking of network connections within the communication infrastructure, specifically affecting the TCP service layer that manages concurrent connections between endpoints and the unified communications platform. The flaw manifests when an attacker establishes a large number of TCP connections to the affected systems, overwhelming the connection tracking mechanisms and causing legitimate services to become unavailable. This vulnerability is categorized under CWE-116 as improper handling of synchronization, specifically in the context of connection state management. The issue affects multiple versions of Cisco's unified communications solutions, with specific patches required for each affected release line including CUCM 5.x before 5.1(3g), 6.x before 6.1(4), 7.0 before 7.0(2), and 7.1 before 7.1(2), as well as Cisco Unified Presence versions 1.x, 6.x before 6.0(6), and 7.x before 7.0(4). The operational impact of this vulnerability can be severe as it directly affects business continuity by causing TCP services to go offline, disrupting voice and video communication services that organizations rely upon for critical operations. Attackers can exploit this weakness by simply creating numerous TCP connections to the target system, causing resource exhaustion and service disruption without requiring authentication or special privileges. The vulnerability aligns with ATT&CK technique T1498 which describes denial of service attacks targeting network services, and more specifically with T1566 which covers credential harvesting through network services. Organizations experiencing this vulnerability may observe symptoms including increased connection timeouts, service unavailability, and complete TCP service outages that can persist until the affected systems are manually restarted or the connection limits are adjusted. The root cause of this issue lies in the insufficient implementation of connection tracking mechanisms that fail to properly manage resource allocation for concurrent TCP connections, leading to a resource exhaustion scenario where legitimate users cannot establish necessary connections to the unified communications platform. This vulnerability represents a fundamental flaw in the system's resource management capabilities and highlights the importance of proper connection handling in mission-critical communication infrastructure.
The technical implementation of this vulnerability demonstrates poor resource management practices within Cisco's unified communications stack, where the system fails to properly limit or throttle incoming TCP connections. The connection tracking mechanisms lack adequate safeguards against connection flooding attacks, allowing an attacker to consume system resources through legitimate TCP connection establishment processes. This design flaw creates a scenario where the system's ability to maintain service availability becomes dependent on the attacker's capacity to establish connections, rather than on proper resource allocation and management. The vulnerability specifically impacts the TCP service layer of these communication platforms, which is responsible for maintaining reliable communication channels between endpoints and the centralized communication infrastructure. When the connection tracking system becomes overwhelmed, it cannot properly manage the state of existing connections or establish new ones, leading to a cascading failure of the TCP service functionality. This type of vulnerability is particularly dangerous in enterprise environments where communication systems are critical for business operations, as it can effectively shut down voice and video communication capabilities across the organization. The lack of proper rate limiting or connection throttling mechanisms in the affected versions means that legitimate users may be unable to establish connections while the system is under attack, creating a denial of service condition that can persist until manual intervention occurs. The vulnerability's impact extends beyond simple service disruption as it affects the core communication infrastructure that many enterprise applications depend upon for their operation.
Mitigation strategies for this vulnerability should focus on implementing proper connection limiting and rate limiting mechanisms at network boundaries, as well as applying the appropriate vendor patches to affected systems. Organizations should configure firewalls and network access control lists to limit the number of concurrent TCP connections from individual sources, effectively preventing the exploitation of this vulnerability through connection flooding attacks. The implementation of connection tracking limits and TCP connection timeouts can provide additional protection against this type of resource exhaustion attack. Network administrators should also consider implementing monitoring solutions that can detect unusual connection patterns and alert administrators to potential exploitation attempts. The recommended remediation approach includes applying the latest security patches provided by Cisco for each affected version, as these patches address the underlying connection tracking implementation flaws. Additionally, organizations should review their network architecture to ensure that connection tracking mechanisms are properly configured to handle expected connection loads while maintaining adequate protection against abnormal connection patterns. The vulnerability's susceptibility to remote exploitation without authentication means that organizations should treat this as a high-priority security concern, regardless of their network segmentation practices. Security teams should also implement network monitoring to detect potential exploitation attempts and establish incident response procedures that include immediate patch deployment and system restart procedures when necessary. This vulnerability underscores the importance of maintaining current security patches and implementing proper network segmentation to limit the impact of such attacks on critical communication infrastructure. The implementation of proper connection tracking and resource management controls serves as a fundamental security measure that protects against not only this specific vulnerability but also similar resource exhaustion attacks targeting other network services.