CVE-2018-7562 in GLPI
Summary
by MITRE
A remote code execution issue was discovered in GLPI through 9.2.1. There is a race condition that allows temporary access to an uploaded executable file that will be disallowed. The application allows an authenticated user to upload a file when he/she creates a new ticket via front/fileupload.php. This feature is protected using different types of security features like the check on the file's extension. However, the application uploads and creates a file, though this file is not allowed, and then deletes the file in the uploadFiles method in inc/glpiuploaderhandler.class.php.
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Analysis
by VulDB Data Team • 02/21/2023
The vulnerability CVE-2018-7562 represents a critical race condition in GLPI versions through 9.2.1 that enables remote code execution through improper file upload handling. This flaw occurs within the file upload functionality exposed through the front/fileupload.php endpoint, where authenticated users can submit files when creating tickets. The vulnerability stems from the application's handling of file validation and deletion processes, creating a temporal window where malicious executable files can temporarily exist on the server before being removed. The race condition arises because the system uploads files immediately upon request while simultaneously checking file extensions and other security parameters. This temporal inconsistency allows attackers to exploit the brief period between file creation and deletion to execute malicious code, as the system's security checks occur after the file has already been written to disk. The flaw specifically manifests in the uploadFiles method within inc/glpiuploaderhandler.class.php, where files are created and then subsequently deleted if they fail validation checks.
The technical implementation of this vulnerability involves a fundamental flaw in the application's file processing pipeline where the security validation occurs after the file has already been committed to storage. This design pattern creates an exploitable window where attackers can upload malicious executables that temporarily bypass the extension validation mechanism. The race condition occurs because the application's file upload process does not properly synchronize the file creation and validation steps, allowing an attacker to potentially execute code during the brief interval between file upload completion and validation failure. This vulnerability aligns with CWE-362, which describes race conditions in security-critical operations, and represents a classic case of improper resource management where temporary files are not adequately secured or isolated during validation processes. The flaw is particularly dangerous because it requires only authenticated access to exploit, meaning that any user with valid credentials can potentially leverage this vulnerability to execute arbitrary code on the server.
The operational impact of CVE-2018-7562 extends beyond simple code execution to encompass full system compromise and potential data breaches. An attacker with authenticated access can upload malicious payloads that persist temporarily during the race condition window, potentially leading to persistent backdoors, privilege escalation, or data exfiltration. The vulnerability affects GLPI installations through version 9.2.1, representing a significant security gap in an asset management and IT service management platform that typically handles sensitive organizational data. This flaw undermines the integrity of the application's security model by allowing authenticated users to bypass file upload restrictions, potentially enabling attackers to gain unauthorized access to the underlying server infrastructure. The attack surface is particularly concerning given that GLPI systems often store confidential information including user credentials, system configurations, and business-critical data, making successful exploitation a serious threat to organizational security.
Mitigation strategies for CVE-2018-7562 require immediate patching of affected GLPI versions to address the race condition in file upload handling. Organizations should implement comprehensive file validation mechanisms that prevent file creation until all security checks have been completed, eliminating the temporal window that enables exploitation. The recommended approach involves synchronizing file upload and validation processes to ensure that files are never written to storage until all security parameters are verified. Additionally, implementing proper file access controls and restricting file upload permissions can reduce the potential impact of successful exploitation attempts. Organizations should also consider implementing network-based detection mechanisms to monitor for suspicious file upload activities and establish robust logging practices to track file handling operations. The vulnerability highlights the importance of proper resource management and synchronization in security-critical applications, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage, as attackers could leverage the executed code to establish persistent access or escalate privileges within the compromised environment.