CVE-2011-2560 in Unified Communications Manager
Summary
by MITRE
The Packet Capture Service in Cisco Unified Communications Manager (aka CUCM, formerly CallManager) 4.x does not properly handle idle TCP connections, which allows remote attackers to cause a denial of service (memory consumption and restart) by making many connections, aka Bug ID CSCtf97162.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability described in CVE-2011-2560 affects Cisco Unified Communications Manager version 4.x, specifically targeting the Packet Capture Service component. This service is designed to capture and analyze network traffic for diagnostic and monitoring purposes within unified communications environments. The flaw manifests in how the system manages TCP connections that remain inactive or idle over extended periods, creating a significant security and operational risk for organizations relying on Cisco's communication infrastructure.
The technical root cause of this vulnerability lies in the improper handling of idle TCP connections within the Packet Capture Service. When numerous TCP connections are established and then left idle, the system fails to properly terminate or reclaim the memory resources associated with these connections. This memory management deficiency allows an attacker to exploit the service by creating many simultaneous connections and maintaining them in an idle state. The cumulative effect of these unmanaged connections leads to progressive memory consumption until the system reaches critical resource exhaustion levels, ultimately causing the service to crash and restart automatically.
This vulnerability presents a substantial operational impact as it enables a remote denial of service attack that can severely disrupt unified communications services. Organizations utilizing Cisco Unified Communications Manager may experience complete service outages when the Packet Capture Service becomes overwhelmed with idle connections, affecting voice and video communication capabilities across the enterprise. The attack requires minimal resources from the attacker while generating maximum disruption, making it particularly dangerous in production environments where communication reliability is critical. The automatic restart behavior of the service compounds the impact by potentially causing temporary service interruptions and loss of ongoing communications.
The vulnerability aligns with CWE-400, which addresses "Uncontrolled Resource Consumption" or "Resource Exhaustion" in software systems. This classification reflects the core issue where the system fails to properly manage and limit resource allocation for idle connections, allowing attackers to consume system resources indefinitely. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique for "Network Denial of Service" and potentially T1566.001 for "Phishing" if the attack is part of a broader compromise strategy. Organizations should implement immediate mitigations including connection timeout configurations, rate limiting for new connection requests, and monitoring for unusual connection patterns. Cisco released specific patches and configuration recommendations to address this vulnerability, emphasizing the importance of keeping unified communications infrastructure updated with security patches to prevent exploitation of such memory management flaws.