CVE-2021-28658 in Django
Summary
by MITRE • 04/06/2021
In Django 2.2 before 2.2.20, 3.0 before 3.0.14, and 3.1 before 3.1.8, MultiPartParser allowed directory traversal via uploaded files with suitably crafted file names. Built-in upload handlers were not affected by this vulnerability.
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Analysis
by VulDB Data Team • 11/16/2024
The vulnerability identified as CVE-2021-28658 represents a critical directory traversal flaw within Django's MultiPartParser component affecting multiple versions of the popular web framework. This issue arises from inadequate input validation during file upload processing, specifically when handling multipart form data containing specially crafted filenames that contain directory traversal sequences such as ../ or ..\\. The vulnerability exists in Django versions 2.2 prior to 2.2.20, 3.0 prior to 3.0.14, and 3.1 prior to 3.1.8, making it a widespread concern across several major releases. The flaw allows attackers to manipulate file upload destinations and potentially overwrite critical system files or place malicious content in unintended directories.
The technical implementation of this vulnerability stems from the MultiPartParser's failure to properly sanitize filenames during file upload processing. When users submit files through web forms that utilize multipart encoding, Django's parser is responsible for handling the incoming data and saving files to the designated storage location. The vulnerability occurs because the parser does not adequately validate or normalize filenames that contain directory traversal sequences, allowing malicious actors to specify paths that extend beyond the intended upload directory. This weakness specifically affects the default file upload handling mechanisms and does not impact custom upload handlers that implement proper validation. The flaw aligns with CWE-22, which categorizes directory traversal vulnerabilities as weaknesses that allow attackers to access files or directories outside the intended scope through manipulation of input data.
The operational impact of CVE-2021-28658 extends beyond simple unauthorized file access, potentially enabling full system compromise through various attack vectors. An attacker could leverage this vulnerability to overwrite critical application files, inject malicious code into the web server, or gain access to sensitive configuration files that might contain database credentials or cryptographic keys. The vulnerability also opens possibilities for privilege escalation attacks, especially when applications run with elevated permissions or when the upload directory is located in a system-critical path. Additionally, this flaw could be combined with other vulnerabilities to create more sophisticated attack scenarios, making it particularly dangerous in environments where multiple security controls are in place. The impact is amplified by the fact that this vulnerability affects core Django functionality, meaning that virtually any application using Django's built-in file upload handling is at risk.
Mitigation strategies for CVE-2021-28658 should prioritize immediate patching of affected Django versions to the latest stable releases containing the fix. Organizations must ensure that all Django installations are updated to versions 2.2.20, 3.0.14, or 3.1.8 respectively, as these releases contain the necessary security patches. Beyond patching, developers should implement additional defensive measures including filename sanitization at the application level, restricting upload directories to minimal necessary permissions, and implementing proper access controls for uploaded files. Security monitoring should be enhanced to detect suspicious file upload patterns, and input validation should be strengthened to prevent directory traversal sequences from being processed. The vulnerability demonstrates the importance of following security best practices such as those outlined in the OWASP Top Ten, particularly focusing on secure file handling and input validation. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation, while ensuring that file upload functionality is properly tested and validated in security testing environments before deployment.