CVE-2019-1887 in Unified Communications Manager
Summary
by MITRE
A vulnerability in the Session Initiation Protocol (SIP) protocol implementation of Cisco Unified Communications Manager could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to insufficient validation of input SIP traffic. An attacker could exploit this vulnerability by sending a malformed SIP packet to an affected Cisco Unified Communications Manager. A successful exploit could allow the attacker to trigger a new registration process on all connected phones, temporarily disrupting service.
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Analysis
by VulDB Data Team • 10/18/2023
The vulnerability identified as CVE-2019-1887 represents a critical flaw in Cisco Unified Communications Manager's handling of Session Initiation Protocol traffic, exposing organizations to potential disruption of their voice communication infrastructure. This issue stems from inadequate input validation mechanisms within the SIP protocol implementation, creating an avenue for remote attackers to manipulate the system's registration processes. The vulnerability specifically affects Cisco Unified Communications Manager versions that process SIP messages without proper sanitization of incoming traffic, making it particularly dangerous in enterprise environments where unified communications systems form the backbone of business operations.
The technical exploitation of this vulnerability occurs through the deliberate crafting of malformed SIP packets that bypass standard validation checks implemented by the Cisco Unified Communications Manager. When these malformed packets are received, the system fails to properly validate the incoming SIP traffic, leading to a cascading effect that triggers registration processes across all connected telephony devices. This behavior manifests as a denial of service condition where legitimate users experience temporary disruption of their communication services as the system becomes overwhelmed with processing invalid registration requests. The flaw operates at the protocol level, targeting the fundamental mechanisms that manage SIP session establishment and maintenance, making it particularly insidious as it affects core communication infrastructure rather than just application-level functions.
From an operational perspective, this vulnerability creates significant risk for organizations relying on Cisco Unified Communications Manager for their voice services, as the DoS condition can result in substantial business disruption during critical communication periods. The attack requires minimal privileges and can be executed remotely without authentication, making it accessible to a wide range of threat actors. The impact extends beyond simple service interruption, as the system's attempt to process malformed registration requests can consume significant processing resources and potentially trigger additional system instability. Organizations may experience cascading failures where the initial DoS condition leads to further system degradation, affecting not just telephony services but potentially other integrated communication systems that depend on the Unified Communications Manager platform.
Mitigation strategies for CVE-2019-1887 should focus on implementing network-level protections and applying official Cisco security patches as recommended in their advisory. Organizations should deploy network access control measures to filter SIP traffic at network boundaries, particularly targeting ports commonly used for SIP communications such as UDP 5060 and TCP 5060. The implementation of SIP-specific firewalls or security appliances that can validate SIP message integrity and detect malformed packets provides an additional layer of protection. Cisco recommends upgrading to affected software versions that include enhanced input validation mechanisms and improved SIP traffic processing capabilities. Additionally, organizations should implement monitoring solutions that can detect unusual registration patterns and alert administrators to potential exploitation attempts, as the vulnerability's impact is often characterized by rapid and repeated registration requests that deviate from normal usage patterns. This vulnerability aligns with CWE-20, which addresses "Improper Input Validation," and represents a specific implementation weakness that could be exploited through techniques consistent with ATT&CK tactic TA0043, which focuses on "Reconnaissance" and "Resource Hijacking" through service disruption mechanisms.
The broader implications of this vulnerability extend to organizational security posture, as it demonstrates the critical importance of validating all incoming protocol traffic and implementing defense-in-depth strategies for communication infrastructure. Organizations should conduct comprehensive assessments of their unified communications environments to identify all systems potentially affected by similar input validation weaknesses, as this class of vulnerability can often manifest across multiple components of communication platforms. Regular security assessments and vulnerability management processes become essential for maintaining protection against such protocol-level attacks that can compromise fundamental infrastructure services. The vulnerability also highlights the necessity of maintaining current security patches and implementing automated update mechanisms for critical communication systems to prevent exploitation of known weaknesses in telephony infrastructure components.