Vulnerability Report

CVE-2021-21994

Title: Authentication Bypass

Authentication Bypass

Proof Of Concept

PoC Available for CVE-2021-21994

CWE Category CWE-287

Published Date Jul 13, 2021

Modified Date Oct 31, 2025

Exploit Status Available

Score 9.8 CVSS v3.1

Exploit Probability (EPSS)

1.16%

Vulnerability Summary

CVE-2021-21994: 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.

Impacted Vendors

vmware 1

Reference Links

https://www.vmware.com/security/advisories/VMSA-2021-0014.html https://www.vmware.com/security/advisories/VMSA-2021-0014.html

CVSS v3.1

Source Entity [email protected]

Severity CRITICAL

9.8

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v2.0

Source Entity [email protected]

Severity MEDIUM

6.8

Access Vector

N/A

Authentication

N/A

RAW VECTOR AV:N/AC:M/Au:N/C:P/I:P/A:P

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2021-21994 Exploits & PoCs (Proof Of Concept)

GitHub https://github.com/mreza-en/cve-2021-21994_POC

View Code

October 31, 2025 MODIFIED

Vulnerability data or affected products updated.

July 13, 2021 PUBLISHED

Vulnerability first announced in NVD.

Attack Vector Matrix

Access Vector NETWORK

Complexity LOW

Privileges N/A

Interaction NONE

CVSS Vector String


                                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Stack

No specific products linked.