CVE-2018-18315 in lemon
Summary
by MITRE
com/mossle/cdn/CdnController.java in lemon 1.9.0 allows attackers to upload arbitrary files because the copyMultipartFileToFile method in CdnUtils only checks for a ../ substring, and does not validate the file type and spaceName parameter.
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Analysis
by VulDB Data Team • 05/25/2023
The vulnerability identified as CVE-2018-18315 resides within the lemon 1.9.0 web application framework, specifically in the com/mossle/cdn/CdnController.java component. This flaw represents a critical security weakness that enables remote attackers to execute arbitrary file uploads, potentially leading to complete system compromise. The vulnerability stems from inadequate input validation mechanisms within the file upload processing pipeline, creating an exploitable path for malicious actors to bypass security controls and deploy unauthorized code or data within the target system.
The technical implementation of this vulnerability occurs through the copyMultipartFileToFile method located in the CdnUtils class, which demonstrates a fundamental flaw in security validation logic. The method performs only a rudimentary check for the presence of "../" substrings in file paths, failing to implement comprehensive validation of file types, directory traversal patterns, or namespace parameters. This insufficient validation creates a path traversal vulnerability that allows attackers to manipulate file upload destinations and potentially write files to arbitrary locations within the application's file system. The absence of proper file type validation means that attackers can upload executable files, scripts, or malicious binaries that could be executed by the web server or application.
The operational impact of this vulnerability extends beyond simple unauthorized file uploads, as it provides attackers with a potential foothold for further exploitation within the target environment. An attacker could leverage this vulnerability to upload web shells, malicious scripts, or other payloads that could be executed by the web server, leading to complete system compromise. The vulnerability affects the application's content delivery network functionality, potentially allowing attackers to modify or replace legitimate content, inject malicious code into the application's delivery pipeline, or establish persistent access points within the system. This type of vulnerability directly relates to CWE-22 Path Traversal and CWE-434 Unrestricted Upload of File with Dangerous Type, both of which are classified as high-risk security weaknesses in the CWE database.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and sanitization measures throughout the file upload processing pipeline. Organizations should implement strict file type validation that checks file extensions, MIME types, and file content signatures rather than relying on simple substring matching. The copyMultipartFileToFile method must be enhanced to validate all parameters including spaceName, file paths, and destination directories against a whitelist of acceptable values. Additionally, the application should implement proper directory traversal protection mechanisms that prevent access to parent directories and enforce strict file path validation. Security controls should include implementing secure file upload restrictions, setting appropriate file permissions, and establishing proper logging and monitoring for file upload activities. These measures align with ATT&CK technique T1059 Command and Scripting Interpreter and T1566 Phishing, as they address the fundamental security weakness that enables attackers to establish persistent access through malicious file uploads.