CVE-2021-21994

published 2021-07-13

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…

Priority P2 66 critical 9.8 CVSS 3.1

AV N AC L PR N UI N S U C H I H A H

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

5 ranges

Vendor	Product	Version range	Fixed in
vmware	cloud_foundation	>= 3.0 < 3.10.2	3.10.2
vmware	cloud_foundation	>= 4.0 < 4.3	4.3
vmware	esxi	—	—
vmware	esxi	—	—
vmware	esxi	—	—

Detection & IOCs extracted from sources · hover to see the quote

port 5989↗

• → Monitor for unexpected or unauthenticated connections to TCP port 5989 (SFCB/CIM Broker) on ESXi hosts, which may indicate exploitation attempts of the authentication bypass vulnerability. ↗
• → Alert on any specially crafted requests targeting the SFCB (Small Footprint CIM Broker) service on ESXi that result in successful authentication without valid credentials. ↗

• · Exploitation requires network-level access to port 5989 on the ESXi host; restricting or firewalling this port reduces attack surface. ↗
• · Affected products include VMware ESXi, VMware Cloud Foundation, and VMware vSphere — all deployments of these products running SFCB should be assessed. ↗

CVSS provenance

nvd v3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd v2.0 6.8 MEDIUM AV:N/AC:M/Au:N/C:P/I:P/A:P

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CWE-287