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CVE-2021-21985

VMware vCenter Server Improper Input Validation

9.8 CRITICALActively exploited (CISA KEV)Used in ransomwarePublic exploitEPSS 100.0%
  1. Published26 May 2021
  2. Added to CISA KEV3 Nov 2021
  3. Remediation due17 Nov 2021
Actively exploited (CISA KEV)

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.

Added to KEV: 3 Nov 2021Federal remediation due: 17 Nov 2021Used in ransomware

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

VMware Cloud Foundation≥ 3.0 < 3.10.2.1 · ≥ 4.0 < 4.2.1
VMware Vcenter Server6.5 · 6.7 · 7.0

Remediation

Fixed in
VMware Cloud Foundation≥ 3.10.2.1

References

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Frequently asked

Is CVE-2021-21985 being actively exploited?

Yes. CVE-2021-21985 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 3 Nov 2021. It has been used in ransomware campaigns.

How severe is CVE-2021-21985?

CVE-2021-21985 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 100.0% probability of exploitation.

Which products are affected by CVE-2021-21985?

Affected products include VMware Cloud Foundation, VMware Vcenter Server.

How do I fix CVE-2021-21985?

Upgrade affected software to a fixed version, for example VMware Cloud Foundation 3.10.2.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-21985 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.