CVE-2019-16385 in Thinfinity VirtualUI
Summary
by MITRE
Cybele Thinfinity VirtualUI 2.5.17.2 allows HTTP response splitting via the mimetype parameter within a PDF viewer request, as demonstrated by an example.pdf?mimetype= substring. The victim user must load an application request to view a PDF, containing the malicious payload. This results in a reflected XSS payload being executed.
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Analysis
by VulDB Data Team • 06/05/2020
Cybele Thinfinity VirtualUI version 2.5.17.2 contains a critical vulnerability that enables HTTP response splitting through improper input validation in the mimetype parameter of PDF viewer requests. This vulnerability exists within the application's handling of user-supplied data when processing PDF documents through the virtualized UI environment. The flaw manifests when a malicious user crafts a specially formatted request containing a crafted mimetype parameter that includes newline characters or other delimiter sequences typically used to separate HTTP headers. The vulnerability is particularly dangerous because it operates within the context of a PDF viewer component that is commonly used in web applications, making it accessible through standard user interactions.
The technical implementation of this vulnerability stems from inadequate sanitization of the mimetype parameter in the application's request processing pipeline. When a victim user loads a PDF document through the VirtualUI interface, the application constructs HTTP responses based on user-provided parameters without proper validation of the mimetype value. This allows an attacker to inject malicious content that can be interpreted as additional HTTP headers, effectively splitting the HTTP response and enabling various attack vectors including cross-site scripting. The vulnerability specifically exploits the way the application handles the PDF viewer request processing, where the mimetype parameter is directly incorporated into HTTP response headers without proper encoding or validation.
The operational impact of this vulnerability extends beyond simple XSS execution to encompass a broader range of potential attacks within the context of the virtualized application environment. An attacker can leverage this vulnerability to inject malicious JavaScript code that executes in the victim's browser context, potentially leading to session hijacking, data theft, or further exploitation of the compromised user session. The attack requires user interaction through loading a malicious PDF request, but once triggered, the reflected XSS payload can execute within the security context of the VirtualUI application. This vulnerability is particularly concerning in enterprise environments where VirtualUI is used for remote desktop and application virtualization, as it could allow attackers to compromise user sessions and potentially gain access to sensitive corporate applications.
The vulnerability maps directly to CWE-113, which describes improper neutralization of CRLF (Carriage Return Line Feed) sequences in HTTP responses, and aligns with ATT&CK technique T1212 for exploitation of web application vulnerabilities. Mitigation strategies should include immediate patching of the VirtualUI application to version 2.5.17.3 or later, which addresses this specific vulnerability through proper input validation and sanitization of HTTP headers. Additionally, organizations should implement web application firewalls to detect and block suspicious HTTP header sequences, and conduct thorough input validation across all user-supplied parameters in the application's request processing. Network segmentation and monitoring of HTTP traffic can help detect exploitation attempts, while user education regarding suspicious PDF requests can reduce successful attack vectors. The vulnerability demonstrates the critical importance of proper HTTP response handling and input validation in web applications, particularly those that process user-supplied data in contexts where HTTP headers are constructed dynamically.