CVE-2007-1833 in Unified CallManager
Summary
by MITRE
The Skinny Call Control Protocol (SCCP) implementation in Cisco Unified CallManager (CUCM) 3.3 before 3.3(5)SR2a, 4.1 before 4.1(3)SR4, 4.2 before 4.2(3)SR1, and 5.0 before 5.0(4a)SU1 allows remote attackers to cause a denial of service (loss of voice services) by sending crafted packets to the (1) SCCP (2000/tcp) or (2) SCCPS (2443/tcp) port.
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Analysis
by VulDB Data Team • 07/17/2019
The vulnerability described in CVE-2007-1833 represents a critical denial of service weakness within Cisco Unified CallManager's implementation of the Skinny Call Control Protocol. This protocol serves as the primary communication mechanism between Cisco IP phones and the call manager system, making it a fundamental component of enterprise voice infrastructure. The affected versions of CUCM processed incoming packets on two specific ports: SCCP on TCP port 2000 and SCCPS on TCP port 2443, both of which are standard endpoints for SCCP communication. The flaw stems from insufficient input validation and packet processing mechanisms that fail to properly handle malformed or specially crafted data sequences sent by unauthorized network entities.
The technical nature of this vulnerability resides in the protocol parser's inability to gracefully handle malformed packets that contain unexpected data structures or buffer overflows within the SCCP message format. When the affected CUCM systems receive these crafted packets, the processing logic encounters unexpected conditions that cause the call manager to crash or become unresponsive, effectively terminating all active voice services for the duration of the disruption. This behavior aligns with CWE-121, which describes buffer overflow conditions, and CWE-122, which addresses improper restriction of operations within a limited memory buffer. The vulnerability specifically targets the protocol state machine that manages phone registration, call setup, and call control functions, making it particularly dangerous for enterprise environments where voice communication is mission-critical.
The operational impact of this vulnerability extends far beyond simple service interruption, as it can affect entire enterprise communication infrastructures and potentially compromise business continuity. Organizations relying on Cisco Unified CallManager for their voice services would experience immediate loss of telephony functionality, affecting employees, customers, and emergency communication pathways. The remote exploitability means that attackers need only access to the network segment where the CUCM servers reside, making the attack surface relatively broad and the potential impact severe. This vulnerability directly maps to ATT&CK technique T1499.004, which describes network denial of service attacks, and represents a classic example of how protocol-level flaws can cascade into enterprise-wide communication outages.
Mitigation strategies for this vulnerability require immediate implementation of network segmentation and access controls to restrict traffic to the affected SCCP ports. Organizations should deploy firewall rules that limit access to TCP ports 2000 and 2443 to only trusted IP addresses and network segments. The most effective long-term solution involves applying the vendor-supplied patches that address the input validation issues in the SCCP protocol implementation, specifically targeting the versions mentioned in the CVE description. Network administrators should also implement monitoring solutions to detect unusual traffic patterns on these ports and establish automated alerting mechanisms for potential exploitation attempts. Additionally, organizations should consider implementing intrusion detection systems with signature-based detection capabilities specifically designed to identify SCCP-related attack patterns, as well as conducting regular vulnerability assessments to identify and remediate similar protocol-level weaknesses in their communication infrastructure.