External risk intelligence

VMware vCenter Server Plugin Remote Code Execution.

CVE advisoryKnown Exploit

CVE-2021-21972

This vulnerability affects vCenter Server, a management application that is typically deployed within internal, protected data center networks. While it is network-reachable via port 443 in some configurations, it is not designed to be a public-facing internet service, and its exposure is generally restricted by enterprise security controls.

Path Traversal

Vmware Cloud Foundation

3.0 to before 3.10.1.24.0 to before 4.26.56.77.0

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability exists within a plugin for the vSphere Client in vCenter Server. This flaw allows an unauthorized individual with network access to execute commands with elevated privileges on the server's operating system. Such an exploit could lead to a significant compromise of the affected environment.

Vulnerable vCenter Server plugin
Unrestricted command execution
Compromise of operating system

Attack Path

How an attacker could exploit the issue

A vulnerability exists in the vSphere Client that allows for remote code execution. A malicious actor could exploit this by accessing a vCenter Server over the network. Successful exploitation would grant the attacker the ability to run commands with unrestricted privileges on the server's operating system. This could lead to significant business risk, impacting system integrity and data confidentiality.

External network access required.
Attacker sends malicious request.
Attacker gains system control.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability allows for the execution of commands with unrestricted privileges on the operating system hosting vCenter Server. Attackers can exploit this through network access to port 443, potentially leading to widespread compromise. Organizations using affected versions of VMware vCenter Server or Cloud Foundation should consider this a high-priority concern.

Attacker skill level: Low
Required access or conditions: Network access to port 443
Business risk or urgency: Critical

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in VMware vCenter Server allows for remote code execution with unrestricted privileges. Organizations using affected versions should take immediate steps to identify and mitigate the risk. This includes verifying which systems are running vulnerable versions, reducing their exposure if possible, and applying the vendor-provided fixes. Following these actions, it is crucial to validate that the fixes have been successfully applied and to monitor for any related security incidents.

Find affected VMware assets.
Reduce exposure or isolate risk.
Fix, verify, and monitor.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is the nature of the vulnerability in VMware vCenter Server's vSphere Client plugin?

A vulnerability exists in a vCenter Server plugin for the vSphere Client that allows for remote code execution. A malicious actor with network access to port 443 could exploit this to run commands with unrestricted privileges on the underlying operating system.

What weakness class does CVE-2021-21972 represent, and what is its impact?

This vulnerability is classified under CWE-22, which relates to improper limitation of a pathname to a restricted directory or a sequence of directory components. Its impact allows an attacker to execute commands with unrestricted privileges on the host operating system, leading to a significant compromise.

What is the trigger path for this vulnerability, and can its scope be limited?

The trigger path involves an attacker with network access to port 443 sending a malicious request. Successful exploitation grants the attacker unrestricted command execution on the server's operating system, potentially leading to a significant compromise of the environment.

How relevant is CVE-2021-21972, considering its exposure and potential for exploitation?

CVE-2021-21972 is highly relevant due to its critical severity and network-accessible nature. While typically deployed in internal networks, its remote code execution capability presents a significant risk. The CISA added it to the Known Exploited Vulnerabilities Catalog, indicating active exploitation.

What are the practical steps for addressing the VMware vCenter Server vulnerability?

To address this vulnerability, organizations should first identify all affected VMware assets. If possible, reduce their exposure or isolate the risk. The primary remediation is to apply vendor-provided fixes, followed by verification of successful application and ongoing monitoring for related security incidents.

References

www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE…

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.