CVE-2019-9972 in Phone System
Summary
by MITRE • 06/07/2022
PhoneSystem Terminal in 3CX Phone System (Debian based installation) 16.0.0.1570 allows an authenticated attacker to run arbitrary commands with the phonesystem user privileges because of " followed by " mishandling.
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Analysis
by VulDB Data Team • 06/10/2022
The CVE-2019-9972 vulnerability affects the 3CX Phone System version 16.0.0.1570 running on Debian-based installations, presenting a critical command injection flaw within the PhoneSystem Terminal component. This vulnerability stems from improper handling of double quotes in user input, creating a path for authenticated attackers to execute arbitrary commands with limited phone system user privileges. The issue manifests when the system processes user-supplied input containing double quotes without adequate sanitization or escaping mechanisms, allowing malicious payloads to be interpreted as shell commands rather than benign data.
The technical exploitation of this vulnerability requires an authenticated user session within the 3CX Phone System environment, making it less severe than fully unauthenticated exploits but still highly dangerous in compromised environments. Attackers can leverage this flaw to execute commands on the underlying Debian system with the privileges of the phonesystem user, which typically has access to phone system configuration files, network interfaces, and potentially sensitive telephony data. The vulnerability specifically relates to improper input validation and sanitization practices that fail to properly escape or quote user-provided data before incorporating it into shell command executions, creating a classic command injection attack vector.
From an operational perspective, this vulnerability poses significant risks to organizations relying on 3CX Phone Systems for their communication infrastructure. The authenticated nature of the exploit means that attackers must first gain valid credentials, but once obtained, they can escalate their privileges to execute arbitrary code on the phone system server. This could lead to complete system compromise, data exfiltration, or disruption of critical telephony services. The phonesystem user privileges, while limited, may still provide access to sensitive configuration data, call logs, and potentially allow attackers to manipulate phone system settings or establish persistence within the network environment. Organizations using this version of 3CX Phone System should immediately assess their authentication controls and implement additional monitoring for suspicious command execution patterns.
The vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and can be categorized under ATT&CK technique T1059.001 for command and scripting interpreter. This weakness represents a fundamental flaw in input validation and command construction practices that should be addressed through proper parameterization of shell commands, implementation of input sanitization, and adherence to secure coding practices. Organizations should ensure that all user-provided input is properly escaped or quoted before being incorporated into system commands, and that privilege separation is maintained to limit the potential impact of such vulnerabilities. The affected 3CX Phone System version represents a specific instance where these security controls were insufficient, highlighting the importance of regular security updates and comprehensive vulnerability management programs.