CVE-2021-21985
VMware vCenter Server Improper Input Validation Vulnerability
- Critical 9.8
- Exploited: added to CISA KEV 3 Nov 2021
- Used in ransomware campaigns
Description
The vSphere Client (HTML5) contains a remote code execution vulnerability due to lack of input validation in the Virtual SAN Health Check plug-in which is enabled by default in vCenter Server. 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.
Key facts
- Published
- 26 May 2021
- Last changed
- 12 Aug 2026
- Assigned by
- vmware
- KEV added
- 3 Nov 2021
- KEV fix due
- 17 Nov 2021
- Used in ransomware
- Yes, according to CISA
- EPSS
- 99.999% likely to be exploited in the next 30 days, higher than 99.993% of CVEs (scores for 15 Nov 2026)
- SSVC (CISA)
- Exploitation: active; Automatable: yes; Technical impact: total
Severity scores
Each score is shown as its source gave it. They are not averaged or merged.
- 9.8CVSS 3.1, Criticalfrom CISA (ADP container)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
What to do
- Apply updates per vendor instructions.CISA KEV required action
Historical context and remediation
This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.
No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.
Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.
Affected products
| Vendor | Product | Versions |
|---|---|---|
| n/a | VMware vCenter Server and VMware Cloud Foundation |
|
Timeline
- 26 May 2021 Published
- 3 Nov 2021 CVE-2021-21985 added to CISA KEV
- 3 Nov 2021 Added to the CISA KEV catalogue