CVE-2021-22016 in vCenter Server
Summary
by MITRE • 09/24/2021
The vCenter Server contains a reflected cross-site scripting vulnerability due to a lack of input sanitization. An attacker may exploit this issue to execute malicious scripts by tricking a victim into clicking a malicious link.
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Analysis
by VulDB Data Team • 10/02/2021
The vulnerability identified as CVE-2021-22016 represents a critical reflected cross-site scripting flaw within VMware vCenter Server, a widely deployed enterprise virtualization management platform. This vulnerability stems from insufficient input sanitization mechanisms that fail to properly validate and escape user-supplied data before incorporating it into web responses. The affected system processes HTTP requests without adequate protection against malicious input, creating an exploitable condition where attacker-controlled data can be reflected back to users in web pages. The security implications are severe as this flaw exists at the core of VMware's vCenter Server infrastructure, which serves as the central management interface for VMware vSphere environments.
The technical exploitation of this vulnerability occurs through the manipulation of HTTP parameters in web requests to the vCenter Server interface. When a user visits a maliciously crafted URL containing attacker-controlled script code, the server reflects this content back to the victim's browser without proper sanitization. This reflected script execution can occur in various contexts including error messages, search results, or any user-controllable input field within the web interface. The vulnerability specifically affects the server-side processing of web requests where input parameters are directly echoed back to users without appropriate HTML encoding or validation. This flaw aligns with CWE-79 which defines improper neutralization of input during web page generation as a primary cause of cross-site scripting vulnerabilities.
The operational impact of CVE-2021-22016 extends beyond simple script execution as it provides attackers with a potential foothold for more sophisticated attacks within enterprise environments. Successful exploitation could enable attackers to steal session cookies, perform unauthorized administrative actions, or redirect users to malicious sites. The vulnerability's presence in vCenter Server creates a particularly dangerous scenario since this platform typically operates with elevated privileges and controls access to critical virtual infrastructure components. Attackers could leverage this flaw to gain unauthorized access to virtual machines, modify configurations, or extract sensitive data from the virtualized environment. This vulnerability directly maps to several ATT&CK techniques including initial access through malicious links and privilege escalation via web application exploitation.
Organizations should prioritize immediate mitigation of this vulnerability through official VMware patches released in response to the security advisory. The recommended remediation includes applying the latest security updates to vCenter Server installations and implementing network-level protections such as web application firewalls to detect and block malicious requests. Additional defensive measures should include monitoring for suspicious web requests containing script payloads and implementing strict input validation policies for all web applications. Security teams should also consider implementing multi-factor authentication and least privilege access controls to limit the potential impact of successful exploitation. Regular vulnerability assessments and penetration testing should be conducted to identify similar issues in other components of the virtual infrastructure stack. The vulnerability highlights the critical importance of input validation in web applications and demonstrates how seemingly minor oversights in sanitization can create severe security risks in enterprise management platforms.