CVE-2021-21972
VMware vCenter Server Remote Code Execution Vulnerability
VMware vCenter Server
The vSphere Client (HTML5) contains a remote code execution vulnerability in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue to execute commands with unrestricted privileges on the underlying operating system that hosts vCenter Server. This affects VMware vCenter Server (7.x before 7.0 U1c, 6.7 before 6.7 U3l and 6.5 before 6.5 U3n) and VMware Cloud Foundation (4.x before 4.2 and 3.x before 3.10.1.2).
Ransomware groups exploiting CVE-2021-21972
The Akira ransomware group is said to have emerged in March 2023, and there's much speculation about its ties to the former CONTI ransomware group. It's worth noting that with the end of CONTI's operation, several affiliates migrated to independent campaigns s
Exploitation is attributed to these groups across their recorded activity. It does not follow that every organisation they listed was reached through CVE-2021-21972 — the source data does not record an entry point per incident.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 3 November 2021. US federal agencies were required to remediate it by 17 November 2021. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 99.5%, which is higher than 99.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Recent listings by these groups
Disclosures from the groups above, newest first.
Frequently asked questions
Is CVE-2021-21972 being exploited by ransomware groups?
Yes. CVE-2021-21972 is recorded as exploited by Akira. Between them these groups account for 1,407 victim disclosures in this database. CISA also records this vulnerability as used in ransomware campaigns.
What does CVE-2021-21972 affect?
CVE-2021-21972 affects VMware vCenter Server. The vSphere Client (HTML5) contains a remote code execution vulnerability in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue to execute commands with unrestricted privileges on the underlying operating system that hosts vCenter Server. This affects VMware vCenter Server (7.x before 7.0 U1c, 6.7 before 6.7 U3l and 6.5 before 6.5 U3n) and VMware Cloud Foundation (4.x before 4.2 and 3.x before 3.10.1.2).
How severe is CVE-2021-21972?
CVE-2021-21972 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 99.5%, higher than 99.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 17 November 2021.
How should organisations respond to CVE-2021-21972?
Apply the vendor patch for VMware vCenter Server as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.