CVE-2021-21994

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-07-13 · updated 2026-06-17
Weakness: CWE-287

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.

Affected products

VMware Cloud Foundation: from 3.0 before 3.10.2; from 4.0 before 4.3 — fixed in 3.10.2, 4.3
VMware ESXi: 6.5-650-201701001, 6.5-650-201703001, 6.5-650-201703002, 6.5-650-201704001, 6.5-650-201707101, 6.5-650-201707102 (+227); 6.5, 6.7, 7.0
VMware ESXi and VMware Cloud Foundation: VMware ESXi(7.0 before ESXi70U2-17630552, 6.7 before ESXi670-202103101-SG, 6.5 before ESXi650-202107401-SG) and VMware Cloud Foundation (4.x, 3.x before 3.10.2)

How to fix

Upgrade to a fixed version: VMware Cloud Foundation 3.10.2, 4.3. Check the vendor advisory for mitigations.

References

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