CVE-2011-4019 in Unified Communications Manager
Summary
by MITRE
Memory leak in Cisco IOS 12.4 and 15.0 through 15.2, and Cisco Unified Communications Manager (CUCM) 7.x, allows remote attackers to cause a denial of service (memory consumption) via a crafted response to a SIP SUBSCRIBE message, aka Bug IDs CSCto93837 and CSCtj61883.
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Analysis
by VulDB Data Team • 01/12/2018
The vulnerability described in CVE-2011-4019 represents a critical memory leak flaw affecting Cisco IOS versions 12.4 and 15.0 through 15.2, alongside Cisco Unified Communications Manager versions 7.x. This issue specifically targets the Session Initiation Protocol (SIP) implementation within these systems, creating a remote denial of service condition through carefully crafted SIP SUBSCRIBE messages. The vulnerability stems from insufficient memory management during the processing of SIP subscription requests, allowing attackers to consume system resources progressively until service availability is compromised. The flaw manifests when the affected systems receive malformed SIP responses that trigger improper memory allocation and subsequent failure to release allocated memory segments, leading to gradual memory exhaustion.
The technical implementation of this vulnerability involves the improper handling of SIP SUBSCRIBE message responses within the Cisco IOS and CUCM platforms. When a malicious actor sends a crafted SIP SUBSCRIBE response, the system allocates memory to process the message but fails to properly deallocate the memory resources upon completion of the processing cycle. This memory allocation pattern creates a cumulative leak that grows with each malicious message received, ultimately exhausting available memory resources and causing the targeted system to become unresponsive. The vulnerability operates at the application layer of the network stack, specifically within the SIP processing components of the communication infrastructure, making it particularly dangerous for voice and video communication systems that rely heavily on SIP protocols.
From an operational perspective, this vulnerability poses significant risks to enterprise communication networks and service providers who depend on Cisco's networking and unified communications solutions. The remote nature of the attack means that adversaries can exploit the flaw from outside the network perimeter without requiring authentication or physical access to the affected systems. The memory consumption aspect of the vulnerability makes it particularly effective for sustained denial of service attacks, as the system gradually becomes less responsive over time rather than experiencing immediate failure. Organizations using affected Cisco products face potential disruptions to voice services, video conferencing, and other SIP-based communication services, which could result in business continuity issues and service degradation for end users.
The mitigation strategies for this vulnerability encompass several approaches that align with established cybersecurity frameworks and best practices. Network administrators should prioritize applying the relevant Cisco security patches and updates that address the memory leak in the SIP processing components. Additionally, implementing network segmentation and access control measures can limit the attack surface by restricting unauthorized access to SIP processing services. The implementation of monitoring and alerting systems that track memory usage patterns can help detect anomalous behavior indicative of exploitation attempts. Organizations should also consider deploying intrusion detection systems that can identify and block malformed SIP traffic patterns. According to CWE classification, this vulnerability maps to CWE-404, which describes improper resource management, and aligns with ATT&CK technique T1499.004 for network denial of service attacks, emphasizing the importance of proper memory management and resource allocation in network infrastructure components.
The impact of this vulnerability extends beyond immediate service disruption to encompass broader implications for network security posture and operational resilience. Organizations that fail to address this memory leak vulnerability may find their communication systems increasingly vulnerable to more sophisticated attack vectors that could leverage the weakened state of the affected platforms. The cumulative nature of the memory consumption means that even brief exposure to malicious traffic can lead to significant resource depletion over time, making regular system monitoring and maintenance essential. Security teams should also consider the potential for cascading effects where compromised communication systems could impact other network services or trigger additional vulnerabilities in interconnected systems, highlighting the importance of comprehensive vulnerability management programs that address both immediate threats and long-term security hygiene practices.