CVE-2020-24583 in Django
Summary
by MITRE
An issue was discovered in Django 2.2 before 2.2.16, 3.0 before 3.0.10, and 3.1 before 3.1.1 (when Python 3.7+ is used). FILE_UPLOAD_DIRECTORY_PERMISSIONS mode was not applied to intermediate-level directories created in the process of uploading files. It was also not applied to intermediate-level collected static directories when using the collectstatic management command.
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Analysis
by VulDB Data Team • 11/12/2020
This vulnerability affects the Django web framework and represents a privilege escalation issue stemming from improper directory permission handling during file operations. The flaw exists in Django versions prior to 2.2.16, 3.0.10, and 3.1.1 when running on Python 3.7 or higher. The vulnerability specifically targets the FILE_UPLOAD_DIRECTORY_PERMISSIONS setting which is designed to control the permissions of directories created during file uploads. When users upload files through Django applications, the framework creates intermediate directories to store these files. However, the system fails to apply the configured permission modes to these automatically generated intermediate directories, creating potential security risks for applications that rely on strict access controls.
The technical implementation of this vulnerability lies in how Django handles directory creation during file upload processes and static file collection operations. During normal file upload workflows, Django creates a hierarchy of directories to store uploaded files, but it only applies the configured FILE_UPLOAD_DIRECTORY_PERMISSIONS to the final target directory while neglecting to set appropriate permissions on the intermediate directories in the path. Similarly, when executing the collectstatic management command to gather static files, the same issue occurs with intermediate directories created during the static file collection process. This behavior creates a security gap where intermediate directories may inherit default system permissions rather than the restricted permissions specified by the application developer. The vulnerability is particularly concerning because it allows for potential information disclosure and privilege escalation attacks, as attackers could potentially access or modify files stored in these improperly secured intermediate directories.
The operational impact of this vulnerability extends beyond simple permission misconfigurations and can significantly compromise application security. Applications that rely on strict access controls for uploaded files or static assets may become vulnerable to unauthorized access if intermediate directories are created with overly permissive permissions. Attackers could exploit this weakness to gain access to files that should be restricted, potentially leading to data breaches or further exploitation of the application. The vulnerability affects the principle of least privilege, as the system fails to enforce the intended permission model throughout the entire directory hierarchy. This issue particularly impacts web applications where users can upload files or where static assets are collected and served, making it a critical concern for applications handling sensitive data. The vulnerability is classified under CWE-276, which deals with incorrect permissions for a resource, and aligns with ATT&CK technique T1078.1.1, which covers legitimate credentials for privilege escalation.
Mitigation strategies for this vulnerability require immediate patching of affected Django versions to the recommended secure releases. Organizations should upgrade their Django installations to versions 2.2.16, 3.0.10, or 3.1.1, depending on their current version, to ensure proper handling of intermediate directory permissions. Additionally, administrators should conduct thorough audits of their file upload and static collection processes to identify any existing improperly secured directories that may have been created prior to the patch implementation. Security monitoring should be enhanced to detect unusual access patterns or permission changes in directory structures, particularly during file upload operations. Organizations should also consider implementing additional security controls such as mandatory access controls or file system integrity monitoring to provide defense-in-depth against potential exploitation of this vulnerability. Regular security assessments and penetration testing should be conducted to ensure that permission settings are properly enforced throughout the application's file handling processes and that no similar issues exist in other components of the system.