CVE-2016-7840 in WEB SCHEDULE
Summary
by MITRE
Cross-site scripting vulnerability in WEB SCHEDULE allows remote attackers to inject arbitrary web script or HTML via the month parameter.
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Analysis
by VulDB Data Team • 09/21/2020
The vulnerability identified as CVE-2016-7840 represents a classic cross-site scripting flaw within the WEB SCHEDULE application that exposes users to potential malicious code execution. This issue specifically affects the month parameter handling within the web interface, creating an avenue for remote attackers to inject arbitrary web scripts or HTML content. The vulnerability stems from inadequate input validation and output sanitization mechanisms that fail to properly filter or escape user-supplied data before it is rendered in the browser context. Such a flaw fundamentally compromises the application's security posture by enabling attackers to execute malicious scripts in the context of authenticated users' browsers, potentially leading to session hijacking, data theft, or further exploitation of the affected system.
The technical implementation of this vulnerability aligns with CWE-79, which categorizes cross-site scripting as a weakness where untrusted data is improperly incorporated into web pages without proper sanitization or encoding. The month parameter serves as the attack vector where malicious input can be passed through URL parameters or form fields, bypassing the application's security controls. When the application processes this parameter without adequate validation, it directly incorporates the user-supplied content into the HTML response, creating an XSS condition. The attack typically involves crafting a malicious payload that includes script tags or other HTML elements that execute when the page renders, exploiting the trust relationship between the user's browser and the vulnerable application.
The operational impact of CVE-2016-7840 extends beyond simple script injection, as it enables attackers to perform various malicious activities within the context of the vulnerable application. Attackers can leverage this vulnerability to steal session cookies, redirect users to malicious sites, deface web pages, or harvest sensitive information from authenticated sessions. The remote nature of the attack means that exploitation does not require physical access to the system or network, making it particularly dangerous for web applications that handle sensitive data or provide privileged access to users. Depending on the application's functionality and user permissions, successful exploitation could lead to complete account compromise or unauthorized access to restricted resources, potentially affecting multiple users if the vulnerability exists in a widely-used scheduling system.
Mitigation strategies for CVE-2016-7840 should focus on implementing robust input validation and output encoding mechanisms throughout the application's data processing pipeline. The most effective approach involves sanitizing all user-supplied input, particularly parameters like month, through proper encoding before rendering in web pages. This includes implementing context-specific encoding such as HTML entity encoding for web page content, JavaScript encoding for dynamic script generation, and URL encoding for parameter values. Additionally, developers should implement Content Security Policy headers to limit the sources from which scripts can be loaded and executed, providing an additional layer of protection against XSS attacks. The implementation of proper input validation frameworks and regular security code reviews can help prevent similar vulnerabilities from emerging in future development cycles, aligning with ATT&CK technique T1213 for credential access through web application vulnerabilities and addressing the broader category of web application security weaknesses. Organizations should also consider implementing web application firewalls and regular penetration testing to identify and remediate similar vulnerabilities across their web infrastructure.