CVE-2021-40191 in Dzzoffice
Summary
by MITRE • 10/11/2021
Dzzoffice Version 2.02.1 is affected by cross-site scripting (XSS) due to a lack of sanitization of input data at all upload functions in webroot/dzz/attach/Uploader.class.php and return a wrong response in content-type of output data in webroot/dzz/attach/controller.php.
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Analysis
by VulDB Data Team • 10/14/2021
The vulnerability CVE-2021-40191 affects Dzzoffice Version 2.02.1 and represents a critical cross-site scripting flaw that stems from inadequate input sanitization within the application's file upload functionality. This vulnerability specifically resides in the webroot/dzz/attach/Uploader.class.php file where all upload functions fail to properly validate or sanitize user-supplied data before processing. The flaw creates an environment where malicious actors can inject malicious scripts into the application's upload mechanisms, potentially compromising user sessions and enabling unauthorized access to sensitive data.
The technical implementation of this vulnerability demonstrates poor security practices in data validation and output handling within the application's attachment processing system. When users upload files through the vulnerable functions in Uploader.class.php, the system does not adequately sanitize the input parameters, allowing attackers to craft malicious payloads that can be executed in the context of other users' browsers. This weakness is particularly dangerous because it affects all upload functions within the application's attachment system, creating a broad attack surface that can be exploited across multiple file types and upload scenarios.
The operational impact of this vulnerability extends beyond simple script execution, as it can be leveraged to perform session hijacking, data theft, and privilege escalation attacks within the Dzzoffice application. Attackers can craft malicious files that, when uploaded and subsequently accessed by other users, will execute arbitrary JavaScript code in their browsers. This can lead to unauthorized access to user accounts, data exfiltration, and potential lateral movement within the application's environment. The vulnerability's presence in the controller.php file, where incorrect content-type responses are returned, further compounds the security risk by potentially enabling additional attack vectors related to content manipulation and response handling.
From a cybersecurity framework perspective, this vulnerability aligns with CWE-79 (Cross-site Scripting) and represents a classic example of insecure input handling that violates fundamental security principles. The flaw also maps to several ATT&CK techniques including T1566 (Phishing) and T1059 (Command and Scripting Interpreter) as attackers can use this vulnerability to establish persistent access through malicious file uploads. The vulnerability demonstrates a critical failure in the principle of least privilege and input validation, where the application trusts user input without proper sanitization before processing.
Mitigation strategies for this vulnerability must address both the immediate code-level fixes and broader architectural security improvements. The primary remediation involves implementing comprehensive input sanitization and validation within the Uploader.class.php file, ensuring all user-supplied data is properly escaped and validated before being processed or stored. Security patches should enforce strict content-type validation in controller.php to prevent incorrect response handling that could be exploited. Organizations should also implement proper output encoding for all user-supplied content and establish automated security testing processes to identify similar vulnerabilities in other application components. Additionally, regular security audits and penetration testing should be conducted to ensure that input validation mechanisms remain robust against evolving attack techniques. The vulnerability highlights the importance of following secure coding practices and implementing defense-in-depth strategies to protect against common web application security flaws.