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.

Published: 2021-07-13 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-21994 is rated Moderate Risk (62/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 1.16%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-21994

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.38% 1.16% +0.78%
2 2026-01-05 0.24% 0.38% +0.14%
3 2025-11-21 — 0.24% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-21994

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-21994

Affected software / configurations for CVE-2021-21994

Vendor Product Version Raw CPE
vmware cloud_foundation >= 3.0, < 3.10.2 cpe:2.3:a:vmware:cloud_foundation:*:*:*:*:*:*:*:*
vmware cloud_foundation >= 4.0, < 4.3 cpe:2.3:o:vmware:cloud_foundation:*:*:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:-:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201701001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201703001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201703002:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201704001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707101:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707102:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707103:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707201:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707202:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707203:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707204:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707205:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707206:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707207:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707208:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707209:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707210:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707211:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707212:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707213:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707214:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707215:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707216:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707217:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707218:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707219:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707220:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201707221:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201710001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201712001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201803001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201806001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201808001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201810001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201810002:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201811001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201811002:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201811301:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201901001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201903001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201905001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201908001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201910001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-20191004001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201911001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201911401:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201911402:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912002:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912101:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912102:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912103:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912104:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912301:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912401:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912402:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912403:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-201912404:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202005001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202006001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202007001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202010001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202011001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202011002:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202102001:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202102002:*:*:*:*:*:*
vmware esxi 6.5 cpe:2.3:o:vmware:esxi:6.5:650-202102003:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:-:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201806001:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201807001:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201808001:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201810001:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201810101:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201810102:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201810103:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201810201:*:*:*:*:*:*
vmware esxi 6.7 cpe:2.3:o:vmware:esxi:6.7:670-201810202:*:*:*:*:*:*

References for CVE-2021-21994

cvelogic Threat Intelligence