Is CVE-2021-21994 actively exploited?

No active exploitation of CVE-2021-21994 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-21994 be exploited remotely?

Yes. CVE-2021-21994 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-21994?

CVE-2021-21994 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2021-21994

CWE-287Published: July 13, 2021· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official Description

SFCB (Small Footprint CIM Broker) as used in ESXi has an authentication bypass vulnerability. A malicious actor with network access to port 5989 on ESXi may exploit this issue to bypass SFCB authentication by sending a specially crafted request.

NVD Source

Technical Analysis

CVE-2021-21994 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

From a weakness classification perspective (CWE-287): Authentication bypass vulnerabilities allow attackers to access protected resources without valid credentials.