CVE-2021-21973 : Security Advisory and Response

A Server Side Request Forgery (SSRF) vulnerability was discovered in the vSphere Client (HTML5) of VMware products, allowing unauthorized network access to vCenter Server plugins. Attackers with access to port 443 could exploit this flaw to disclose sensitive information.

Understanding CVE-2021-21973

This CVE impacts VMware vCenter Server versions 7.x before 7.0 U1c, 6.7 before 6.7 U3l, 6.5 before 6.5 U3n, and VMware Cloud Foundation versions 4.x before 4.2, 3.x before 3.10.1.2.

What is CVE-2021-21973?

The vulnerability in the vSphere Client (HTML5) arises from inadequate URL validation in vCenter Server plugins, enabling SSRF attacks. Threat actors could exploit the flaw by sending a POST request to the plugin, leading to information leakage.

The Impact of CVE-2021-21973

The SSRF vulnerability in VMware products could be leveraged by malicious entities to gain unauthorized access to restricted data, potentially resulting in data breaches and other security incidents.

Technical Details of CVE-2021-21973

The exploit allows attackers to manipulate the vCenter Server plugin through network requests to port 443, bypassing URL validation mechanisms and accessing sensitive information.

Vulnerability Description

The SSRF vulnerability in the vSphere Client (HTML5) of VMware products permits unauthorized network access to vCenter Server plugins, potentially compromising the confidentiality of sensitive data.

Affected Systems and Versions

VMware vCenter Server versions 7.x (before 7.0 U1c), 6.7 (before 6.7 U3l), 6.5 (before 6.5 U3n), and VMware Cloud Foundation versions 4.x (before 4.2), 3.x (before 3.10.1.2) are all susceptible to CVE-2021-21973.

Exploitation Mechanism

Threat actors exploiting CVE-2021-21973 can gain unauthorized access to the vCenter Server plugin by sending malicious POST requests over the network to port 443, circumventing URL validation checks. This could lead to the exposure of sensitive information.

Mitigation and Prevention

Organizations and users can take immediate steps to secure their VMware environments and protect against potential exploitation of CVE-2021-21973.

Immediate Steps to Take

It is crucial to apply security patches promptly, update VMware products to the latest versions, monitor network traffic for suspicious activity, and restrict access to sensitive plugins to mitigate the risk associated with CVE-2021-21973.

Long-Term Security Practices

Implementing stringent network controls, conducting regular security assessments, and maintaining awareness of emerging threats can enhance the long-term security posture of VMware infrastructures.

Patching and Updates

Regularly check for security advisories from VMware, apply patches as soon as they are released, and prioritize updating vulnerable versions to secure the environment against known vulnerabilities like CVE-2021-21973.