CVE-2011-0941 in Unified Communications Manager
Summary
by MITRE
Memory leak in Cisco Unified Communications Manager (CUCM) 6.x before 6.1(5)su2, 7.x before 7.1(5b)su3, 8.x before 8.0(3a)su1, and 8.5 before 8.5(1), and Cisco IOS 12.4 and 15.1, allows remote attackers to cause a denial of service (memory consumption and process failure or device reload) via a malformed SIP message, aka Bug IDs CSCti75128 and CSCtj09179.
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Analysis
by VulDB Data Team • 02/13/2019
Cisco Unified Communications Manager versions 6.x through 8.5 and Cisco IOS 12.4 and 15.1 contain a memory leak vulnerability in their Session Initiation Protocol handling mechanisms that enables remote attackers to consume system resources and trigger denial of service conditions. This vulnerability specifically affects the processing of malformed SIP messages which causes the affected systems to continuously allocate memory without proper deallocation, leading to progressive memory exhaustion. The flaw exists within the SIP message parsing and processing components of these telecommunications platforms, where insufficient input validation and memory management practices allow maliciously crafted SIP packets to trigger memory allocation sequences that are never properly released back to the system. The vulnerability manifests when the system receives malformed SIP messages that contain unexpected or malformed parameters that cause the SIP stack to allocate memory for processing but fail to clean up these allocations upon encountering parsing errors or invalid message structures. This memory leak can accumulate over time and eventually lead to complete system failure, requiring manual intervention or automatic device reloads to restore normal operations.
The technical implementation of this vulnerability aligns with CWE-401, which describes improper management of memory allocation and deallocation in software systems. The flaw represents a classic resource exhaustion attack vector where attackers can repeatedly send malformed SIP messages to consume available memory resources until the system reaches critical memory thresholds. The impact extends beyond simple resource consumption to include complete system instability and potential service disruption that affects enterprise communication infrastructure. The vulnerability affects multiple versions across different Cisco product lines, indicating a fundamental flaw in the SIP processing implementation that was not adequately addressed across the affected release branches. The specific Bug IDs CSCti75128 and CSCtj09179 reference internal tracking systems that document the precise conditions under which memory leaks occur during SIP message processing. From an operational perspective, this vulnerability provides attackers with a straightforward method to disrupt communication services without requiring elevated privileges or complex attack chains, making it particularly dangerous in enterprise environments where continuous availability of communication systems is critical.
The operational impact of this vulnerability extends to enterprise communication networks where Cisco Unified Communications Manager serves as the core telephony infrastructure. When exploited, the memory leak causes progressive system degradation that can lead to complete service outages affecting voice communications, video conferencing, and collaboration services. The vulnerability enables attackers to cause denial of service conditions that may require manual intervention to resolve, including system restarts or memory cleanup operations that can result in significant downtime for critical business communications. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter without requiring physical access or network credentials, making it particularly concerning for organizations with limited network segmentation. The attack vector through malformed SIP messages represents a common exploitation technique that leverages the widespread use of SIP protocol in VoIP communications, where even small flaws in message processing can have significant operational consequences. Organizations affected by this vulnerability may experience cascading failures as memory exhaustion propagates through system components, potentially affecting not only the primary communication services but also related network infrastructure components that depend on stable system resources. The vulnerability's persistence across multiple release versions indicates that the underlying memory management issues were not properly addressed in the software development lifecycle, suggesting potential gaps in testing and quality assurance processes for telecommunications software components.
Mitigation strategies for this vulnerability include immediate application of Cisco security patches and updates that address the memory leak in SIP processing components. Organizations should implement network segmentation and access controls to limit exposure of affected systems to untrusted networks and implement monitoring solutions to detect unusual memory consumption patterns that may indicate exploitation attempts. The implementation of SIP message filtering and validation mechanisms at network boundaries can help reduce the attack surface by blocking malformed SIP traffic before it reaches vulnerable systems. Regular system monitoring and memory usage tracking should be implemented to identify early signs of memory exhaustion that could indicate exploitation attempts. Network administrators should also consider implementing rate limiting and connection tracking measures to prevent rapid repeated attacks that could accelerate memory consumption. The vulnerability's classification as a denial of service condition means that organizations should have incident response procedures in place to quickly identify and address exploitation attempts, including automated alerts for memory usage thresholds and system stability metrics. Additionally, organizations should conduct regular security assessments of their telecommunications infrastructure to identify similar vulnerabilities in other network components and ensure comprehensive protection against resource exhaustion attacks that could affect critical business services.