CVE-2006-0368 in Call Manager
Summary
by MITRE
Cisco CallManager 3.2 and earlier, 3.3 before 3.3(5)SR1, 4.0 before 4.0(2a)SR2c, and 4.1 before 4.1(3)SR2 allow remote attackers to (1) cause a denial of service (CPU and memory consumption) via a large number of open TCP connections to port 2000 and (2) cause a denial of service (fill the Windows Service Manager communication queue) via a large number of TCP connections to port 2001, 2002, or 7727.
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Analysis
by VulDB Data Team • 06/23/2025
Cisco CallManager versions 3.2 and earlier, 3.3 before 3.3(5)SR1, 4.0 before 4.0(2a)SR2c, and 4.1 before 4.1(3)SR2 contain significant security vulnerabilities that enable remote attackers to execute denial of service attacks against the system. These vulnerabilities specifically target the TCP connection handling mechanisms within the application's communication ports, creating exploitable conditions that can lead to system resource exhaustion and complete service disruption. The flaw stems from inadequate connection management and resource allocation controls that fail to properly handle excessive concurrent connections. This vulnerability falls under the category of resource exhaustion attacks as classified by the Common Weakness Enumeration framework, specifically mapping to CWE-400 which addresses unchecked resource consumption. The affected ports 2000, 2001, 2002, and 7727 represent critical communication endpoints used by the Cisco CallManager system for various telephony and management functions. When exploited, these vulnerabilities can cause significant operational impact by consuming all available CPU cycles and memory resources, effectively rendering the telephony system unusable for legitimate users.
The technical exploitation of this vulnerability occurs through the systematic establishment of numerous simultaneous TCP connections to the vulnerable ports. Attackers can leverage this technique to flood the system with connection requests, overwhelming the TCP connection handling mechanisms and causing the system to allocate excessive resources to maintain these connections. The port 2000 vulnerability specifically targets the primary communication port, while ports 2001, 2002, and 7727 represent alternative communication channels that also suffer from the same resource exhaustion conditions. This attack vector aligns with the ATT&CK framework's T1498 technique for resource exhaustion, where adversaries consume system resources to prevent legitimate use of services. The Windows Service Manager communication queue filling represents a more sophisticated aspect of the vulnerability, indicating that the system's underlying Windows service architecture is also susceptible to the same resource exhaustion conditions. This demonstrates how the vulnerability extends beyond simple TCP connection management to affect the entire service communication stack.
The operational impact of these vulnerabilities can be severe for organizations relying on Cisco CallManager for their telephony infrastructure. A successful attack can result in complete service disruption, preventing legitimate users from making or receiving calls, accessing voicemail systems, or utilizing other telephony features. The system may become unresponsive or crash entirely, requiring manual intervention and potentially lengthy restart procedures. Organizations may experience significant business disruption during peak usage periods, as the denial of service conditions can affect critical communication channels. The resource consumption patterns can also lead to cascading failures where the system's performance degrades gradually before complete failure occurs, making detection and mitigation more challenging. Network administrators may find it difficult to distinguish between legitimate high-traffic conditions and attack-induced resource exhaustion, complicating incident response efforts. The vulnerability's presence in multiple versions of Cisco CallManager indicates that organizations across different software releases were potentially affected, requiring broad remediation efforts. This vulnerability also highlights the importance of proper connection rate limiting and resource management in telephony systems, as the lack of such controls can lead to complete system compromise through simple resource exhaustion attacks.
Mitigation strategies for this vulnerability should focus on implementing proper connection rate limiting and resource allocation controls at multiple levels. Organizations should deploy network access control lists to restrict access to the vulnerable ports and implement connection rate limiting to prevent excessive concurrent connections. The most effective long-term solution involves upgrading to patched versions of Cisco CallManager, specifically versions 3.3(5)SR1, 4.0(2a)SR2c, and 4.1(3)SR2 or later, which contain the necessary fixes for these resource exhaustion conditions. Network segmentation and firewall rules should be configured to limit access to these ports to only trusted sources, reducing the attack surface. System monitoring should be implemented to detect unusual connection patterns and resource consumption spikes that may indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify and remediate similar issues in other network infrastructure components. Additionally, implementing proper logging and alerting mechanisms can help administrators detect and respond to exploitation attempts more quickly. The remediation process should include thorough testing of the patched systems to ensure that legitimate functionality is not disrupted while addressing the resource exhaustion vulnerabilities. Organizations should also consider implementing intrusion detection systems that can identify and block the specific attack patterns associated with this vulnerability, providing additional layers of protection against similar resource exhaustion attacks.