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01 Record

CVE-2021-21985

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

CriticalKEVPUBLISHEDCNA: vmware
CNA base score9.8 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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02 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

03 Exploitation and scoring

Exploitation
Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalog on 2021-11-03. Federal remediation due 2021-11-17. Known ransomware campaign use: reported by CISA.
SSVC decision
  • ExploitationactiveCISA reports credible evidence of active exploitation.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
99.99% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 99.9% of scored records. A rank, not a probability.
NVD base score
9.8 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD analysis status
Analyzed. NVD last modified this record on 2026-08-12.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2021-05-26 14:04Z5 YR AGO
Last updated
2026-08-12 03:55Z2 MO AGO
Reserved
2021-01-04
Assigning CNA
vmware
Record state
PUBLISHED
Severity
Critical (CVSS 9.8)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weaknesses
  • CWE-20Improper Input ValidationClass
  • CWE-470Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')Base
  • CWE-918Server-Side Request Forgery (SSRF)Base
Data version
5.2
Document digest
c7b2bf42efa952d0c5b4177001b0183b096bf492cefcd3fe96fd2800526c14e9

05 Affected products

VendorProductVersionsPlatforms
n/aVMware vCenter Server and VMware Cloud FoundationVMware vCenter Server (7.x before 7.0 U2b, 6.7 before 6.7 U3n, 6.5 before 6.5 U3p) and VMware Cloud Foundation (4.x before 4.2.1, 3.x before 3.10.2.1)—

06 References