CVE-2019-1676 in Meeting Server
Summary
by MITRE
A vulnerability in the Session Initiation Protocol (SIP) call processing of Cisco Meeting Server (CMS) software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition of the Cisco Meeting Server. The vulnerability is due to insufficient validation of Session Description Protocol (SDP) messages. An attacker could exploit this vulnerability by sending a crafted SDP message to the CMS call bridge. An exploit could allow the attacker to cause the CMS to reload, causing a DoS condition for all connected clients. Versions prior to 2.3.9 are affected.
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Analysis
by VulDB Data Team • 07/09/2023
The vulnerability identified as CVE-2019-1676 represents a critical denial of service weakness within Cisco Meeting Server software that specifically targets the Session Initiation Protocol call processing mechanisms. This flaw exists in the handling of Session Description Protocol messages which are fundamental components in establishing and managing multimedia sessions through SIP infrastructure. The vulnerability stems from inadequate input validation procedures that fail to properly sanitize or verify the structure and content of incoming SDP messages before processing them within the call bridge functionality.
The technical exploitation of this vulnerability occurs through the transmission of specifically crafted SDP messages that manipulate the session description parameters in ways that trigger unexpected behavior within the CMS software. When the system receives these malformed or maliciously constructed SDP messages, the insufficient validation mechanisms fail to detect the anomalous inputs, allowing them to proceed through the normal processing pipeline. This failure results in the CMS call bridge experiencing a condition that forces it to reload its services, effectively disrupting all active connections and rendering the system unavailable to legitimate users. The vulnerability affects all versions prior to 2.3.9, indicating that Cisco had not yet implemented adequate safeguards against this particular class of malformed SDP message processing.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the reliability and availability of enterprise communication systems that depend on Cisco Meeting Server for their video conferencing and collaboration infrastructure. Organizations utilizing affected CMS versions face the risk of unauthorized parties causing widespread service interruptions that could affect business continuity, collaborative workflows, and critical communication channels. The unauthenticated nature of the attack means that any external party with network access to the affected system could potentially exploit this weakness without requiring prior credentials or privileged access, making the vulnerability particularly dangerous in network environments where such access might be limited.
This vulnerability aligns with CWE-20, which describes improper input validation as a fundamental weakness in software security design, and demonstrates how insufficient sanitization of protocol-specific message formats can lead to system instability. From an adversarial perspective, this weakness maps to ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a specific vector through which attackers can achieve persistent service disruption against communication infrastructure. The vulnerability's classification as a remote attack vector without authentication requirements places it within the high-risk category of exploits that can be leveraged by threat actors with minimal access privileges, making it particularly attractive for attackers seeking to disrupt enterprise communication systems.
Cisco addressed this vulnerability through software updates that introduced enhanced SDP message validation procedures and improved error handling within the CMS call processing pipeline. The recommended mitigation involves immediate deployment of software versions 2.3.9 and later, which incorporate additional checks to verify the integrity and structure of incoming SDP messages before they are processed by the call bridge component. Organizations should also implement network segmentation and access controls to limit exposure of CMS systems to untrusted networks, while monitoring for unusual traffic patterns that might indicate exploitation attempts. The fix demonstrates the importance of proper protocol handling and input validation in maintaining system stability and preventing exploitation of fundamental communication infrastructure components.