Critical severity · published Jul 13, 2021
CVE-2021-21994
SFCB (Small Footprint CIM Broker) as used in ESXi has an authentication bypass vulnerability
9.8
CVSS
1.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.2% · higher than 67% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ES
ESXi · VMware
6.5; 6.5; 6.5; 6.5; 6.5; 6.5; +34 more · source: NVD
CF
Cloud Foundation · Vmware
3.0 before 3.10.2 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21994
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-21994
Vendor Advisory
https://www.vmware.com/security/advisories/VMSA-2021-0014.html
More from ESXi
9.8
CVE-2020-3992
VMware ESXi OpenSLP Use-After-Free Vulnerability
9.8
CVE-2019-5544
VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow Vulnerability
8.2
CVE-2025-22225
VMware ESXi Arbitrary Write Vulnerability
8.2
CVE-2025-22224
VMware ESXi and Workstation TOCTOU Race Condition Vulnerability
7.8
CVE-2010-3904
Linux Kernel Improper Input Validation Vulnerability