CVE-2018-16736 in rcfilters Plugin
Summary
by MITRE
In the rcfilters plugin 2.1.6 for Roundcube, XSS exists via the _whatfilter and _messages parameters (in the Filters section of the settings).
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Analysis
by VulDB Data Team • 12/24/2024
The vulnerability identified as CVE-2018-16736 affects the rcfilters plugin version 2.1.6 within the Roundcube webmail platform, representing a cross-site scripting flaw that enables remote attackers to execute malicious scripts in the context of affected user sessions. This vulnerability specifically manifests within the Filters section of the application settings where the plugin processes user input through the _whatfilter and _messages parameters. The rcfilters plugin serves as an extension for managing email filtering rules within Roundcube, making it a critical component for email administration and automation. The vulnerability arises from insufficient input validation and output sanitization mechanisms within the plugin's handling of these specific parameters, creating an attack vector that can be exploited by malicious actors to inject malicious code into the web application's response.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input containing script payloads and submits it through the _whatfilter and _messages parameters within the filter configuration interface. When the vulnerable plugin processes this input without proper sanitization, the malicious code becomes embedded within the application's HTML response and executes in the browser context of authenticated users who view the affected filter settings. This type of vulnerability falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental web application security weakness that allows attackers to inject client-side scripts into web pages viewed by other users. The vulnerability's impact is amplified by the fact that it occurs within the administrative settings section, potentially allowing attackers to escalate privileges or gain unauthorized access to user email accounts.
The operational impact of CVE-2018-16736 extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, data exfiltration, and unauthorized email manipulation. An attacker who successfully exploits this vulnerability can potentially access sensitive email communications, modify filter rules to redirect or delete messages, and establish persistent access to user accounts. The vulnerability affects all users who have administrative access to the Roundcube filter settings, making it particularly dangerous in environments where multiple administrators manage email filtering policies. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: JavaScript, as it leverages JavaScript execution capabilities within the web browser environment. The attack chain typically involves initial access through a vulnerable web application, followed by the injection of malicious JavaScript payloads that can interact with the browser's DOM and potentially leverage additional browser vulnerabilities.
Organizations should implement immediate mitigations including updating the rcfilters plugin to version 2.1.7 or later, which contains the necessary patches to address the input validation issues. Additionally, administrators should implement proper input sanitization measures and output encoding for all user-supplied data within the web application. Network-based mitigations such as web application firewalls can provide additional protection layers, though they should not be considered a complete solution. Security monitoring should include detection of suspicious parameter values in filter configuration endpoints, and regular security audits should verify that no unauthorized modifications have occurred to filter settings. The vulnerability demonstrates the importance of proper input validation and output encoding practices as outlined in OWASP Top Ten categories and should serve as a reminder of the critical need for secure coding practices in web application development. Regular patch management processes should be enforced to ensure timely updates of all third-party plugins and components within webmail systems, as this vulnerability could be exploited by automated scanning tools that target known vulnerable versions of popular webmail plugins.