CVE-2019-9581 in Booked Scheduler
Summary
by MITRE
phpscheduleit Booked Scheduler 2.7.5 allows arbitrary file upload via the Favicon field, leading to execution of arbitrary Web/custom-favicon.php PHP code, because Presenters/Admin/ManageThemePresenter.php does not ensure an image file extension.
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Analysis
by VulDB Data Team • 08/09/2025
The vulnerability identified as CVE-2019-9581 affects phpscheduleit Booked Scheduler version 2.7.5 and represents a critical arbitrary file upload flaw that can lead to remote code execution. This vulnerability stems from insufficient input validation within the theme management functionality of the application. The specific weakness occurs in the Presenters/Admin/ManageThemePresenter.php file where the system fails to properly validate file extensions when processing favicon uploads. This oversight creates a pathway for attackers to upload malicious PHP files disguised as image files, bypassing the intended security controls that should restrict uploads to legitimate image formats only.
The technical implementation of this vulnerability demonstrates a classic improper input validation issue that aligns with CWE-434, which specifically addresses the insecure upload of executable files. Attackers can exploit this weakness by uploading a PHP file with a filename that includes an image extension such as .jpg or .png, but with actual PHP code content. When the application attempts to process this file through the custom-favicon.php endpoint, the server executes the malicious PHP code rather than treating it as a simple image file. This execution occurs because the application does not enforce strict file type validation, instead relying on the file extension alone which can be easily manipulated by attackers.
The operational impact of this vulnerability extends beyond simple code execution to potentially compromise the entire web application and underlying server infrastructure. An attacker who successfully exploits this vulnerability can gain unauthorized access to the system, execute arbitrary commands, and potentially escalate privileges within the application environment. The implications are particularly severe because the vulnerability affects a core administrative function - theme management - which typically requires elevated privileges but can be exploited through a simple file upload mechanism. This vulnerability can result in complete system compromise, data exfiltration, and the establishment of persistent backdoors within the target environment.
Organizations using phpscheduleit Booked Scheduler 2.7.5 should implement immediate mitigations to address this vulnerability. The primary remediation involves implementing strict file type validation in the ManageThemePresenter.php file to ensure that uploaded files are actually image files and not executable code. This can be achieved through multiple validation layers including MIME type checking, file content verification, and enforcement of strict filename extensions. Additionally, the application should implement proper file storage separation, ensuring uploaded files are not executable and are stored in directories that do not allow web execution. The mitigation strategy should also include implementing the principle of least privilege for file upload functionality and establishing proper access controls for administrative features. This vulnerability also maps to ATT&CK technique T1505.003 for server-side include attacks and T1059.007 for scripting languages, highlighting the need for comprehensive defensive measures across multiple attack vectors.