CVE-2019-15517 in Nginx Proxy Manager
Summary
by MITRE
jc21 Nginx Proxy Manager before 2.0.13 allows %2e%2e%2f directory traversal.
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Analysis
by VulDB Data Team • 12/01/2023
The jc21 Nginx Proxy Manager vulnerability CVE-2019-15517 represents a critical directory traversal flaw that enables unauthorized access to sensitive system files through crafted URL parameters. This vulnerability specifically affects versions prior to 2.0.13 of the popular Nginx proxy management tool, which is widely deployed in enterprise environments for reverse proxy configurations and SSL certificate management. The flaw manifests when the application fails to properly sanitize user input containing encoded directory traversal sequences, allowing attackers to manipulate file paths and access restricted directories on the underlying filesystem. The vulnerability is particularly concerning as it directly impacts the security posture of organizations relying on this proxy management solution for their web infrastructure.
The technical implementation of this vulnerability stems from improper input validation within the application's path handling logic. When users submit requests containing the encoded sequences %2e%2e%2f, which represent the directory traversal pattern ../, the application fails to adequately sanitize these inputs before processing file operations. This allows an attacker to craft malicious URLs that can traverse directory structures and access files outside the intended application boundaries. The vulnerability operates at the application layer and can be exploited through HTTP requests without requiring authentication, making it particularly dangerous in environments where the proxy manager is exposed to untrusted networks. According to CWE-22, this represents a classic directory traversal weakness that has been consistently identified as a critical security risk in web applications.
The operational impact of this vulnerability extends beyond simple information disclosure, as successful exploitation can lead to complete system compromise. Attackers can leverage this vulnerability to access configuration files that may contain database credentials, API keys, and other sensitive information. Additionally, the ability to traverse directories opens pathways for arbitrary code execution if the application is configured to serve executable files or if attackers can upload malicious content to writable directories. The vulnerability affects the confidentiality, integrity, and availability of the affected systems, potentially enabling attackers to establish persistent access, escalate privileges, or disrupt services. Organizations using this proxy manager may find their entire web infrastructure at risk, as the compromised system could be used as a pivot point for attacking internal network resources. This vulnerability aligns with ATT&CK technique T1059.007 for command and script interpreter execution and T1566.001 for malicious file execution, demonstrating how directory traversal can serve as a foundational attack vector for broader compromise.
Organizations should immediately upgrade to version 2.0.13 or later to remediate this vulnerability, as no effective workarounds exist for this specific flaw. The patch addresses the input validation issues by implementing proper sanitization of user-supplied paths before file operations are executed. Security teams should conduct comprehensive assessments of their Nginx proxy manager deployments to identify any systems still running vulnerable versions. Network segmentation and access controls should be implemented to limit exposure of the proxy manager to untrusted networks, while monitoring systems should be configured to detect suspicious directory traversal attempts. Regular security audits and vulnerability scanning should include checks for this specific vulnerability, as it may have been exploited in the past without detection. The vulnerability serves as a reminder of the critical importance of keeping web applications updated and maintaining robust input validation controls to prevent directory traversal attacks.