CVE-2015-6931 in vCenter Server
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the vSphere Web Client in VMware vCenter Server 5.0 before U3g, 5.1 before U3d, and 5.5 before U2d allows remote attackers to inject arbitrary web script or HTML via a crafted URL.
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Analysis
by VulDB Data Team • 01/28/2019
The CVE-2015-6931 vulnerability represents a critical cross-site scripting flaw in VMware vCenter Server's vSphere Web Client component, affecting multiple versions including vSphere 5.0 before U3g, 5.1 before U3d, and 5.5 before U2d. This vulnerability resides within the web interface's handling of user-supplied input in URL parameters, creating an attack vector that enables remote exploitation without requiring authentication. The flaw specifically manifests when the web client fails to properly sanitize or encode user-provided data before rendering it within the browser context, allowing malicious actors to inject arbitrary HTML or JavaScript code that executes in the context of other users' sessions.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding mechanisms within the vSphere Web Client's URL processing logic. When users navigate to specially crafted URLs containing malicious payloads, the web client processes these inputs without adequate sanitization, leading to the execution of injected scripts in the victim's browser. This type of vulnerability maps directly to CWE-79 - Improper Neutralization of Input During Web Page Generation, which is categorized under the broader category of injection flaws in the CWE hierarchy. The vulnerability's classification aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: JavaScript, as it enables attackers to execute malicious JavaScript code within user sessions.
The operational impact of this vulnerability is severe as it allows attackers to perform session hijacking, data theft, and privilege escalation within the vSphere environment. An attacker could craft malicious URLs that, when clicked by an authenticated user, would execute scripts to steal session cookies, redirect users to phishing sites, or even modify virtual machine configurations. The remote nature of the attack means that threat actors can exploit this vulnerability from outside the network perimeter, making it particularly dangerous for organizations that expose their vCenter servers to external networks. The vulnerability essentially provides a gateway for attackers to compromise the entire virtual infrastructure managed by vCenter, potentially leading to complete system compromise and data breaches.
Organizations should implement multiple layers of mitigation strategies to address this vulnerability effectively. Immediate remediation involves applying the official VMware patches released for each affected version, which typically include enhanced input validation and output encoding mechanisms. Network-level protections such as web application firewalls should be configured to detect and block suspicious URL patterns containing known XSS attack signatures. Additionally, organizations should implement strict input validation policies that enforce proper encoding of all user-supplied data before processing, along with regular security scanning of web applications to identify similar vulnerabilities. The mitigation approach should also include user education regarding the dangers of clicking untrusted links and implementing role-based access controls to limit the impact of potential exploitation. According to industry best practices outlined in the OWASP Top Ten Project, this vulnerability would be classified as a high-risk issue requiring immediate attention and remediation to prevent unauthorized access to critical virtualization infrastructure.