CVE-2021-45967 in Cloud Phone System
Summary
by MITRE • 03/18/2022
An issue was discovered in Pascom Cloud Phone System before 7.20.x. A configuration error between NGINX and a backend Tomcat server leads to a path traversal in the Tomcat server, exposing unintended endpoints.
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Analysis
by VulDB Data Team • 03/20/2022
The vulnerability identified as CVE-2021-45967 represents a critical configuration flaw within the Pascom Cloud Phone System version 7.19.x and earlier, where improper NGINX server configuration creates a path traversal condition in the backend Tomcat application server. This misconfiguration allows unauthorized users to access sensitive system endpoints that should remain restricted, fundamentally compromising the application's access control mechanisms. The issue stems from a lack of proper input validation and sanitization at the reverse proxy layer, creating an attack surface that exposes internal system resources to external adversaries. The vulnerability manifests when NGINX fails to properly sanitize or validate file paths before forwarding requests to the Tomcat server, enabling attackers to manipulate the path traversal mechanism and gain access to unintended directories and resources.
The technical exploitation of this vulnerability follows a path traversal pattern that aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as directory traversal. Attackers can leverage this flaw by crafting malicious requests that include directory traversal sequences such as ../ or ..\ in their URI paths, allowing them to navigate through the file system hierarchy of the Tomcat server. This configuration error creates a direct pathway for attackers to access sensitive files, configuration data, and system resources that should be protected within the application's intended access boundaries. The vulnerability essentially bypasses the normal access controls that should prevent unauthorized file system access, exposing the backend infrastructure to potential data exfiltration and system compromise.
The operational impact of CVE-2021-45967 extends beyond simple information disclosure, as it provides attackers with the ability to access internal system endpoints that may contain sensitive configuration files, user data, or system credentials. This exposure creates opportunities for further exploitation including potential privilege escalation, data theft, and system disruption. The vulnerability affects the integrity and confidentiality of the Pascom Cloud Phone System, potentially exposing communication data, user credentials, and system configuration details. From an adversarial perspective, this flaw represents a low-effort, high-impact attack vector that can be leveraged for reconnaissance, lateral movement, and persistent access within the affected network infrastructure.
Mitigation strategies for this vulnerability should focus on correcting the NGINX configuration to properly sanitize and validate all incoming requests before forwarding them to the Tomcat backend server. The implementation of proper input validation at the reverse proxy level is essential to prevent path traversal attacks, including the enforcement of strict path validation rules and the removal of dangerous characters or sequences from URI paths. System administrators should implement comprehensive access control policies, regularly audit NGINX configurations, and apply security patches as soon as they become available. The remediation process should include thorough testing of the updated configurations to ensure that legitimate system functionality remains intact while preventing unauthorized access through path traversal mechanisms. Additionally, organizations should consider implementing web application firewalls and intrusion detection systems to monitor for suspicious path traversal attempts and provide additional layers of protection against similar vulnerabilities in the future.