CVE-2021-21994 : Exploit Details and Defense Strategies

SFCB (Small Footprint CIM Broker) in VMware ESXi and VMware Cloud Foundation versions prior to ESXi70U2-17630552, ESXi670-202103101-SG, ESXi650-202107401-SG, and VMware Cloud Foundation (4.x, 3.x before 3.10.2) is affected by an authentication bypass vulnerability. An attacker with network access to port 5989 on ESXi could exploit this issue to bypass SFCB authentication by sending a specially crafted request.

Understanding CVE-2021-21994

This section provides insights into the impact and technical details of CVE-2021-21994.

What is CVE-2021-21994?

CVE-2021-21994 involves an authentication bypass vulnerability in the Small Footprint CIM Broker (SFCB) component utilized in VMware ESXi and VMware Cloud Foundation.

The Impact of CVE-2021-21994

The vulnerability allows a malicious actor with network access to potentially bypass SFCB authentication on ESXi, which could lead to unauthorized access and misuse of the affected systems.

Technical Details of CVE-2021-21994

Below are the technical aspects related to the CVE-2021-21994 vulnerability.

Vulnerability Description

The vulnerability occurs due to an authentication bypass issue within the SFCB component on ESXi that could be exploited by sending a crafted request to port 5989.

Affected Systems and Versions

VMware ESXi versions 7.0 before ESXi70U2-17630552, 6.7 before ESXi670-202103101-SG, 6.5 before ESXi650-202107401-SG, and VMware Cloud Foundation versions 4.x, 3.x before 3.10.2 are impacted by this vulnerability.

Exploitation Mechanism

An attacker with network access to port 5989 on ESXi can exploit this vulnerability by sending a specifically designed request to bypass SFCB authentication.

Mitigation and Prevention

Protect your systems from CVE-2021-21994 with the following measures.

Immediate Steps to Take

Apply the necessary security patches provided by VMware to address the vulnerability.
Monitor network traffic to detect any suspicious activities targeting port 5989.

Long-Term Security Practices

Regularly update and patch your VMware ESXi and VMware Cloud Foundation installations.
Implement network security measures to restrict unauthorized access to critical ports.

Patching and Updates

Keep your systems up to date with the latest security patches released by VMware to mitigate the CVE-2021-21994 vulnerability.