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CVE-2021-21991 Explained : Impact and Mitigation

Discover details of CVE-2021-21991 affecting VMware vCenter Server and Cloud Foundation. Learn the impact, affected versions, and mitigation strategies for this local privilege escalation vulnerability.

A local privilege escalation vulnerability affecting VMware vCenter Server and VMware Cloud Foundation has been identified. An attacker with non-administrative user access on the vCenter Server host could exploit this vulnerability to elevate privileges to Administrator on the vSphere Client or vCenter Server vSphere Web Client.

Understanding CVE-2021-21991

This section will provide insights into the nature and impact of the CVE-2021-21991 vulnerability.

What is CVE-2021-21991?

The CVE-2021-21991 vulnerability is a local privilege escalation issue within VMware vCenter Server and VMware Cloud Foundation. It arises from how the vCenter Server handles session tokens, allowing unauthorized users to escalate their privileges on the vSphere Client or vCenter Server vSphere Web Client.

The Impact of CVE-2021-21991

The vulnerability can be exploited by threat actors with non-administrative user access to the vCenter Server host. They could leverage this flaw to escalate their privileges to the Administrator level on critical components such as the vSphere Client and vCenter Server vSphere Web Client.

Technical Details of CVE-2021-21991

In this section, we will delve into the technical specifics of CVE-2021-21991.

Vulnerability Description

The vulnerability originates from a flaw in how the vCenter Server processes session tokens, leading to the unauthorized elevation of user privileges.

Affected Systems and Versions

VMware vCenter Server versions 7.x before 7.0 U2c, 6.7 before 6.7 U3o, and 6.5 before 6.5 U3q, along with VMware Cloud Foundation versions 4.x before 4.3 and 3.x before 3.10.2.2, are susceptible to this privilege escalation vulnerability.

Exploitation Mechanism

Malicious actors with non-administrative user access on the vCenter Server can exploit this vulnerability to elevate their privileges to the Administrator level on the vSphere Client or vCenter Server vSphere Web Client.

Mitigation and Prevention

This section outlines the steps to mitigate the risks associated with CVE-2021-21991.

Immediate Steps to Take

Organizations should apply security updates provided by VMware to address the vulnerability promptly. Additionally, restrict user access to critical systems and monitor for any unusual activities.

Long-Term Security Practices

Implement proactive security measures such as regular security assessments, user access reviews, and security awareness training to enhance overall cybersecurity posture.

Patching and Updates

Regularly update VMware vCenter Server and VMware Cloud Foundation to the latest versions to ensure that security patches are applied and vulnerabilities are mitigated effectively.

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