CVE-2017-9538 in Network Performance Monitor
Summary
by MITRE
The 'Upload logo from external path' function of SolarWinds Network Performance Monitor version 12.0.15300.90 allows remote attackers to cause a denial of service (permanent display of a "Cannot exit above the top directory" error message throughout the entire web application) via a ".." in the path field. In other words, the denial of service is caused by an incorrect implementation of a directory-traversal protection mechanism.
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Analysis
by VulDB Data Team • 11/21/2019
The vulnerability identified as CVE-2017-9538 resides within the SolarWinds Network Performance Monitor version 12.0.15300.90, specifically affecting the 'Upload logo from external path' functionality. This issue represents a critical directory traversal flaw that enables remote attackers to manipulate the application's file handling mechanisms. The vulnerability manifests when an attacker supplies a path containing ".." sequences in the upload logo function, which should normally be rejected by proper directory traversal protection. The flaw demonstrates a fundamental failure in input validation and path resolution logic, allowing malicious actors to bypass intended security boundaries.
The technical implementation of this vulnerability stems from inadequate sanitization of user-supplied path parameters within the web application's file upload mechanism. When the application processes a path containing directory traversal sequences, it fails to properly validate or normalize the input before attempting to resolve the file path. This improper handling creates a condition where the application cannot correctly determine the intended directory structure, resulting in a permanent denial of service state. The error message "Cannot exit above the top directory" indicates that the application's path resolution algorithm has detected what it interprets as an attempt to traverse beyond the designated root directory, but the implementation is flawed and causes the application to become unresponsive rather than simply rejecting the request.
The operational impact of this vulnerability extends beyond simple service disruption, as it affects the entire web application interface and renders it unusable for legitimate users. The permanent nature of the denial of service means that once exploited, the application cannot be recovered without manual intervention, requiring administrators to restart services or manually correct the application state. This vulnerability directly violates security principles outlined in the CWE taxonomy under CWE-22, which addresses improper limitation of a pathname to a restricted directory. The flaw also aligns with ATT&CK technique T1499.004, which describes network denial of service attacks through manipulation of application logic, and represents a critical weakness in the application's input validation and access control mechanisms.
Mitigation strategies for CVE-2017-9538 should focus on implementing robust input validation and path normalization procedures within the application's file handling components. Organizations should ensure that all user-supplied path parameters undergo strict sanitization, with special attention to directory traversal sequences such as ".." and their variations. The implementation should include comprehensive path resolution checks that validate against a predefined whitelist of allowed directories and reject any input that attempts to traverse beyond the intended scope. Additionally, the application should enforce proper access controls and implement secure coding practices that prevent the execution of malicious path sequences. System administrators should also consider implementing network-level protections such as web application firewalls to detect and block suspicious path traversal attempts, while maintaining regular security updates and patches to address known vulnerabilities in third-party applications like SolarWinds NPM.