CVE-2021-43697 in Workerman-ThinkPHP-Redis
Summary
by MITRE • 11/29/2021
An unspecified version of Workerman-ThinkPHP-Redis is affected by a Cross Site Scripting (XSS) vulnerability. In file Controller.class.php, the exit function will terminate the script and print the message to the user. The message will contain $_GET{C('VAR_JSONP_HANDLER')] then there is a XSS vulnerability.
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Analysis
by VulDB Data Team • 12/02/2021
The vulnerability identified as CVE-2021-43697 affects Workerman-ThinkPHP-Redis, a popular PHP framework combination used for building web applications. This cross site scripting vulnerability stems from improper input validation and output encoding within the Controller.class.php file, where the exit function processes user-supplied data without adequate sanitization. The flaw specifically manifests when the application processes the $_GET['C('VAR_JSONP_HANDLER')'] parameter, which allows attackers to inject malicious scripts into the response. This vulnerability represents a classic XSS attack vector that can be exploited through crafted HTTP requests containing malicious payloads in the affected parameter.
The technical implementation of this vulnerability occurs at the application layer where user input from the $_GET superglobal is directly incorporated into the exit message without proper HTML escaping or sanitization. When the application terminates execution and displays the message to the user, any malicious script content within the VAR_JSONP_HANDLER parameter gets executed within the victim's browser context. This behavior aligns with CWE-79, which defines Cross Site Scripting as the improper handling of input data that allows attackers to inject executable code into web applications. The vulnerability exists because the framework fails to implement proper output encoding mechanisms when rendering user-supplied values in contexts where script execution is possible.
The operational impact of this vulnerability is significant as it allows remote attackers to execute arbitrary JavaScript code in the context of affected web applications. An attacker could leverage this vulnerability to steal session cookies, perform unauthorized actions on behalf of users, redirect victims to malicious sites, or deface web pages. The attack requires minimal prerequisites as it only needs the ability to send HTTP requests with crafted parameters to the vulnerable application. This makes the vulnerability particularly dangerous in environments where the application processes user input from untrusted sources without proper validation. The vulnerability could affect any web application built using the Workerman-ThinkPHP-Redis framework that handles JSONP requests without proper input sanitization.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms throughout the application. The primary fix involves sanitizing all user-supplied input before incorporating it into application output, particularly in contexts where HTML rendering occurs. Developers should implement proper HTML escaping for all dynamic content and avoid direct concatenation of user input into response messages. Additionally, the application should enforce strict parameter validation for JSONP handlers and implement Content Security Policy headers to limit script execution capabilities. Organizations should also consider implementing web application firewalls and regular security scanning to detect similar vulnerabilities in their codebase. This vulnerability demonstrates the importance of following secure coding practices and adhering to the principle of least privilege in web application development, where all user input should be treated as potentially malicious and properly validated before processing.