CVE-2017-18635 in noVNC
Summary
by MITRE
An XSS vulnerability was discovered in noVNC before 0.6.2 in which the remote VNC server could inject arbitrary HTML into the noVNC web page via the messages propagated to the status field, such as the VNC server name.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/10/2024
The CVE-2017-18635 vulnerability represents a cross-site scripting flaw in the noVNC remote desktop application that affected versions prior to 0.6.2. This vulnerability stems from insufficient input sanitization within the status field handling mechanism of the noVNC web interface, creating a pathway for malicious actors to inject arbitrary HTML content into the victim's browser session. The vulnerability specifically manifests when the remote VNC server transmits messages to the status field, including critical information such as the VNC server name, which can contain maliciously crafted payloads that execute within the context of the user's browser.
The technical exploitation of this vulnerability occurs through the improper handling of user-controllable input data within the noVNC web application's status field rendering process. When a remote VNC server sends information that gets displayed in the status area, the application fails to adequately sanitize this data before rendering it in the browser environment. This lack of input validation creates an environment where attackers can inject malicious scripts that execute in the victim's browser context, potentially leading to session hijacking, credential theft, or other malicious activities. The vulnerability is classified as a classic XSS flaw under CWE-79, which specifically addresses the improper neutralization of input during web page generation.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to manipulate the noVNC interface in ways that compromise user security and system integrity. An attacker who gains the ability to inject content into the status field can potentially redirect users to malicious sites, steal session cookies, or execute arbitrary commands within the context of the victim's browser session. This risk is particularly concerning in enterprise environments where remote desktop access is commonly used, as it could provide attackers with persistent access to internal network resources. The vulnerability aligns with ATT&CK technique T1071.004 for application layer protocol usage and T1531 for credential access through session hijacking.
Mitigation strategies for CVE-2017-18635 primarily involve upgrading to noVNC version 0.6.2 or later, which includes proper input sanitization and output encoding mechanisms. Organizations should also implement additional security measures such as content security policies to limit script execution capabilities within the noVNC interface, and consider network-level restrictions to limit exposure to potentially malicious VNC servers. Regular security audits and input validation reviews should be conducted to prevent similar vulnerabilities from emerging in other components of the remote access infrastructure. The fix implemented in version 0.6.2 addresses the root cause by ensuring all user-controllable data passed to the status field is properly escaped and sanitized before rendering in the browser environment, thereby preventing malicious HTML injection attacks.