CVE-2007-5537 in Unified Communications Manager
Summary
by MITRE
Cisco Unified Communications Manager (CUCM, formerly CallManager) 5.1 before 5.1(2), and Unified CallManager 5.0, allow remote attackers to cause a denial of service (kernel panic) via a flood of SIP INVITE messages to UDP port 5060, which triggers resource exhaustion, aka CSCsi75822.
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Analysis
by VulDB Data Team • 07/28/2019
Cisco Unified Communications Manager versions 5.1 before 5.1(2) and Unified CallManager 5.0 contain a critical vulnerability that enables remote attackers to execute denial of service attacks through SIP INVITE message flooding. This vulnerability specifically targets UDP port 5060 which is the standard port for Session Initiation Protocol communications. The flaw occurs when the system receives an excessive number of SIP INVITE requests that overwhelm the kernel resources, leading to a complete system crash known as kernel panic. The vulnerability is catalogued as CSCsi75822 and represents a fundamental design weakness in how the system handles incoming SIP traffic without adequate rate limiting or resource management controls. This issue directly impacts the availability of voice communication services within enterprise networks that rely on Cisco's unified communications infrastructure.
The technical mechanism behind this vulnerability involves the system's failure to properly implement traffic rate limiting or resource allocation controls for SIP protocol handling. When attackers flood the UDP port 5060 with a high volume of INVITE messages, the CUCM system's kernel becomes overwhelmed with processing requests that consume excessive memory and CPU resources. The system lacks proper queuing mechanisms or connection throttling that would normally prevent a single source from consuming all available resources. This type of attack falls under the category of resource exhaustion attacks, which are classified as CWE-400 in the Common Weakness Enumeration framework. The vulnerability demonstrates poor input validation and resource management practices that allow malicious actors to exploit the system's inability to handle abnormal traffic loads gracefully.
The operational impact of this vulnerability extends far beyond simple service disruption, as it can completely compromise the availability of voice communication services within an organization's network infrastructure. When a kernel panic occurs, the entire Cisco Unified Communications Manager system becomes unresponsive, requiring manual intervention and potentially causing extended downtime for all voice services. This affects not only internal communications but also external customer interactions, emergency services, and business continuity operations that depend on reliable voice infrastructure. Organizations using affected versions of CUCM may experience cascading failures where the system crash impacts other integrated network services that depend on the unified communications platform. The vulnerability also creates opportunities for attackers to conduct prolonged denial of service campaigns that can be difficult to detect and mitigate in real-time network environments.
Mitigation strategies for this vulnerability should focus on implementing network-level protections and system hardening measures. Organizations should deploy rate limiting controls at network boundaries to restrict the number of SIP INVITE messages that can be processed per second, effectively preventing the resource exhaustion scenario. Network administrators should consider implementing firewall rules that limit UDP port 5060 access to trusted sources only, while also configuring intrusion detection systems to monitor for unusual traffic patterns. The most effective long-term solution involves upgrading to Cisco Unified Communications Manager version 5.1(2) or later, which includes proper resource management and rate limiting mechanisms that address this specific vulnerability. Additionally, implementing proper network segmentation and monitoring protocols can help detect and respond to such attacks before they cause system-wide failures. This vulnerability highlights the importance of maintaining current security patches and implementing defense-in-depth strategies that protect against both known and emerging threats in unified communications environments. The ATT&CK framework categorizes this type of attack under privilege escalation and denial of service techniques, emphasizing the need for comprehensive network security controls that address multiple attack vectors.