CVE-2026-23697 in Vtiger
Summary
by MITRE • 07/07/2026
Vtiger CRM before 8.4.0 contains an authenticated file upload vulnerability that allows low-privileged users to achieve remote code execution by uploading a .phar file containing arbitrary PHP code through the Documents module, bypassing the extension denylist in config.inc.php which omits the .phar extension. The uploaded file is stored with its original .phar extension under the web-accessible storage directory, and a misconfigured .htaccess using Apache 2.2 syntax is silently ignored on Apache 2.4 deployments, allowing unauthenticated HTTP requests to directly execute the uploaded PHP payload.
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Analysis
by VulDB Data Team • 07/07/2026
This vulnerability exists within vtiger CRM versions prior to 8.4.0 and represents a critical authenticated file upload flaw that enables low-privileged users to achieve remote code execution through the Documents module. The technical implementation involves a bypass of the security restriction mechanism designed to prevent dangerous file extensions from being uploaded. The vulnerability stems from an incomplete extension denylist in the config.inc.php configuration file which fails to include the .phar extension, allowing malicious users to upload PHP files with this specific extension. When users upload files through the Documents module, these files are stored in the web-accessible storage directory with their original .phar extension intact, creating a direct pathway for exploitation.
The operational impact of this vulnerability is severe as it allows attackers with minimal privileges to execute arbitrary code on the target system without requiring authentication for the final payload execution. The exploitation process leverages a combination of misconfigured server settings and flawed security controls where Apache 2.4 deployments silently ignore the .htaccess configuration that would normally prevent direct execution of .phar files. This misconfiguration creates an environment where uploaded PHP payloads can be executed directly through HTTP requests, bypassing normal web application security restrictions. The vulnerability demonstrates poor input validation and inadequate server configuration management practices that collectively enable remote code execution capabilities.
The root cause of this issue aligns with CWE-434 which addresses insecure file upload vulnerabilities, specifically targeting the failure to properly validate file extensions and the lack of proper access controls for uploaded files. From an attack perspective, this vulnerability maps to multiple ATT&CK techniques including T1505.003 (Server Software Component) and T1059.007 (Command and Scripting Interpreter: PowerShell), as it allows adversaries to execute malicious payloads through the web server's PHP processing capabilities. The weakness also corresponds to T1203 (Exploitation for Client Execution) and T1078 (Valid Accounts) since authenticated access is required initially but provides a pathway for privilege escalation or lateral movement within the compromised environment.
Organizations should implement immediate mitigations including updating to vtiger CRM version 8.4.0 or later where the fix addresses the extension denylist bypass, ensuring proper .htaccess configuration files are deployed with Apache 2.4 environments, and implementing additional file validation controls beyond simple extension checking. The recommended approach includes deploying Content Security Policy headers, restricting file upload functionality to specific user roles only, and implementing file type verification mechanisms that check actual file content rather than relying solely on extensions. Server administrators should also verify that all .htaccess files are properly configured for Apache 2.4 compatibility and that web server configurations prevent direct execution of PHP files in upload directories. Additionally, network segmentation and monitoring solutions should be deployed to detect unusual file upload patterns and potential exploitation attempts.