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Vulnerabilities

Vulnerability · CVE-2021-21985

VMware vCenter Server Improper Input Validation Vulnerability

Published May 26, 2021 · catalog updated Aug 11, 2026 · VMware vCenter Server

Patch now

CVE-2021-21985 is in the CISA known-exploited catalog, due Nov 17, 2021. Confirm VMware vCenter Server against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
Critical9.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
100.00%
Remediation
Remediation guidance
Affected products
cpe vmware/cloud foundation · cpe vmware/vcenter server · vendor VMware vCenter Server

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe vmware/cloud foundationversion unspecified
  • cpe vmware/vcenter server6.5
  • vendor VMware vCenter Serverversion unspecified

How to fix CVE-2021-21985

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-21985 is in the CISA known-exploited catalog, due Nov 17, 2021. Confirm VMware vCenter Server against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with vmware/vcenter server 6.5. Apply updates per vendor instructions.

What should an analyst verify?

CWE-20: Improper Input Validation; CWE-470; CWE-918: Server-Side Request Forgery (SSRF). EPSS 100.00%. The CISA KEV listing is the exploitation evidence. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 26, 2021 · Catalog

    Detected

    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.

  2. Nov 3, 2021 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. Nov 17, 2021 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Aug 11, 2026 · Catalog

    Updated

    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.

Sources

  • CISA KEVConfirmed exploitationCVE-2021-21985

    VMware vSphere Client contains an improper input validation vulnerability in the Virtual SAN Health Check plug-in, which is enabled by default in vCenter Server, which allows for remote code execution.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2021-21985

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-21985

    30-day exploitation probability 100.0%

    first.org
  • Metasploit ModulesPublic exploit moduleexploit_linux/http/vmware_vcenter_vsan_health_rce

    Public module reference (excellent). Module source is not copied into this catalog.

    rapid7.com
  • NIST NVDVulnerability recordCVE-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 malicious actor with network access to port 443 may exploit this issue to execute com

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/162812/VMware-Security-Advisory-2021-0010.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/163487/VMware-vCenter-Server-Virtual-SAN-Health-Check-Remote-Code-Execution.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • VulnCheck KEVConfirmed exploitationCVE-2021-21985

    VMware vSphere Client contains an improper input validation vulnerability in the Virtual SAN Health Check plug-in, which is enabled by default in vCenter Server, which allows for remote code execution.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.