CVE-2016-20023 in CKFinder
Summary
by MITRE • 12/05/2025
In CKSource CKFinder before 2.5.0.1 for ASP.NET, authenticated users could download any file from the server if the correct path to a file was provided.
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Analysis
by VulDB Data Team • 12/17/2025
The vulnerability identified as CVE-2016-20023 represents a critical access control flaw within CKSource CKFinder versions prior to 2.5.0.1 for ASP.NET implementations. This issue stems from insufficient validation of file paths and access permissions, allowing authenticated users to bypass normal security controls and retrieve arbitrary files from the server filesystem. The flaw exists in the file download functionality where the application fails to properly verify whether the requesting user has legitimate authorization to access the specified file path, creating a path traversal condition that can be exploited by malicious actors.
The technical implementation of this vulnerability manifests through the application's inadequate input sanitization and access control mechanisms. When authenticated users attempt to download files, the CKFinder component processes the requested file path without sufficient validation against the user's permission levels or the application's configured security policies. This allows attackers to construct malicious file paths that could traverse directories and access files outside of the intended user access boundaries. The vulnerability specifically affects the ASP.NET version of CKFinder, where the server-side file handling logic does not adequately enforce directory restrictions or validate file access permissions before executing download operations.
From an operational perspective, this vulnerability poses significant risks to organizations utilizing CKFinder for content management and file sharing. An authenticated attacker with minimal privileges could potentially access sensitive files including configuration files, database credentials, application source code, and other confidential data stored on the server. The impact extends beyond simple unauthorized file access as it can lead to information disclosure, potential system compromise, and escalation of privileges within the application environment. The vulnerability is particularly dangerous because it requires only authenticated access, meaning that attackers need only obtain valid user credentials or exploit other authentication bypass techniques to gain access to the file system.
The security implications of this vulnerability align with CWE-22, which describes improper limitation of a pathname to a restricted directory, and can be categorized under ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting. Organizations should immediately implement the vendor-provided patch for CKFinder version 2.5.0.1 or later, which addresses the access control bypass by implementing proper path validation and permission checking mechanisms. Additional mitigations include restricting file download capabilities where possible, implementing robust user access controls, and monitoring for unusual file access patterns. Network-level protections such as web application firewalls and strict access controls on the file system can provide additional defense in depth measures to prevent exploitation of this vulnerability.