CVE-2019-20032 in SV8100
Summary
by MITRE
An attacker with access to an InMail voicemail box equipped with the find me/follow me feature on Aspire-derived NEC PBXes, including all versions of SV8100, SV9100, SL1100 and SL2100 devices, may access the system's administration modem.
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Analysis
by VulDB Data Team • 07/30/2020
This vulnerability exists within NEC PBX systems that utilize the Aspire-derived InMail voicemail platform, specifically affecting SV8100, SV9100, SL1100, and SL2100 device models. The flaw stems from insufficient access controls and authentication mechanisms within the find me/follow me feature implementation, which allows unauthorized users with access to a legitimate voicemail box to escalate privileges and gain access to the system's administration modem. The vulnerability represents a critical security weakness that directly violates the principle of least privilege and proper access control enforcement. This issue falls under the CWE-284 access control weakness category, specifically addressing improper access control mechanisms that permit unauthorized system-level access through legitimate user interfaces. The attack vector is particularly concerning as it requires minimal initial compromise - an attacker only needs access to any valid voicemail box with the find me/follow me feature enabled to potentially gain administrative privileges.
The technical exploitation of this vulnerability occurs through a privilege escalation mechanism within the PBX's authentication framework. When a user accesses the find me/follow me feature from a compromised voicemail box, the system fails to properly validate the user's authorization level before granting access to administrative functions. This misconfiguration allows the attacker to bypass normal authentication procedures and directly access the modem interface that typically requires administrative credentials. The underlying flaw likely involves improper session management and insufficient input validation within the application layer that processes these feature requests. The vulnerability creates a direct path from user-level access to system-level administrative control, fundamentally undermining the security architecture of the telephony platform. This represents a classic example of how feature-rich applications can introduce security gaps when proper access control boundaries are not maintained between different privilege levels.
The operational impact of this vulnerability is severe for organizations relying on these PBX systems, as it provides attackers with complete administrative control over the telephony infrastructure. Once compromised, attackers can modify system configurations, intercept communications, manipulate voicemail messages, create new user accounts, and potentially gain access to sensitive business communications. The vulnerability particularly affects enterprise environments where PBX systems handle confidential business data and communications, making it a prime target for both external attackers seeking to compromise business operations and internal threat actors with legitimate access. The administrative modem access enables attackers to potentially modify system parameters, disable security features, or establish persistent access points within the network infrastructure. This vulnerability directly maps to multiple ATT&CK techniques including privilege escalation, persistence mechanisms, and credential access, making it a significant concern for organizations with comprehensive threat modeling requirements.
Organizations should implement immediate mitigations including disabling the find me/follow me feature on affected devices until proper patches are deployed, enforcing strict access controls on voicemail features, and implementing network segmentation to isolate PBX systems from general business networks. System administrators should conduct comprehensive audits of all PBX configurations to identify and disable unnecessary features that could be exploited. The vulnerability highlights the importance of proper security testing and validation of telephony systems, particularly when implementing complex features that interact with system-level functions. Organizations should also consider implementing network monitoring solutions specifically designed to detect anomalous modem access patterns and unauthorized administrative activities. Regular security assessments of telephony infrastructure, including vulnerability scanning and penetration testing, should be conducted to identify similar access control weaknesses in other network components. The incident underscores the necessity of maintaining up-to-date security patches and implementing defense-in-depth strategies that protect critical infrastructure components from both external and internal threats.