CVE-2006-5553 in Security Agent
Summary
by MITRE
Cisco Security Agent (CSA) for Linux 4.5 before 4.5.1.657 and 5.0 before 5.0.0.193, as used by Unified CallManager (CUCM) and Unified Presence Server (CUPS), allows remote attackers to cause a denial of service (resource consumption) via a port scan with certain options.
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Analysis
by VulDB Data Team • 04/25/2026
Cisco Security Agent version 4.5 before 4.5.1.657 and 5.0 before 5.0.0.193 contains a vulnerability that enables remote attackers to perform denial of service attacks through carefully crafted port scanning activities. This vulnerability specifically affects the Linux implementation of CSA that is integrated within Cisco Unified CallManager and Unified Presence Server environments, creating a critical operational weakness in enterprise communication infrastructures. The flaw manifests when certain port scan options are employed against systems running the vulnerable CSA versions, leading to excessive resource consumption that ultimately results in system unresponsiveness or complete service disruption.
The technical nature of this vulnerability stems from insufficient input validation and resource management within the CSA component's packet processing mechanisms. When legitimate port scanning activities are conducted with specific flag combinations or scan patterns, the agent fails to properly handle the incoming network traffic, causing memory allocation issues and CPU resource exhaustion. This behavior aligns with CWE-400, which categorizes unchecked resource allocation as a fundamental weakness in software design that can lead to denial of service conditions. The vulnerability specifically exploits the agent's inability to efficiently process and discard malformed or excessive network packets during scanning operations, creating a resource starvation scenario that impacts system availability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire communication infrastructures within enterprise environments. Unified CallManager and Unified Presence Server deployments that utilize the vulnerable CSA versions become susceptible to attacks that can render voice and messaging services unavailable to users. Attackers can exploit this weakness through remote network access without requiring authentication credentials, making the attack surface particularly concerning for organizations that rely on these critical communication platforms. The vulnerability affects systems where CSA is deployed as a security agent, which typically operates at the network level to monitor and control access to enterprise resources, creating a potential attack vector that could impact business continuity and operational efficiency.
Organizations affected by this vulnerability should immediately implement the vendor-provided security patches and updates to address the resource consumption issues within the Cisco Security Agent. The recommended mitigation strategy involves upgrading to CSA versions 4.5.1.657 or later, or 5.0.0.193 or later, which contain fixes for the identified resource handling flaws. Network administrators should also consider implementing additional monitoring and intrusion detection measures to identify and block suspicious scanning activities targeting the affected systems. From an ATT&CK framework perspective, this vulnerability maps to techniques involving resource exhaustion and denial of service, specifically covering the T1499.004 sub-technique related to network denial of service attacks. Organizations should also review their network security policies to ensure that access controls are properly configured to limit exposure to such attacks while maintaining necessary communication functionality.