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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Nov 2021. Known ransomware use
Cloud FoundationApplication · VMware

CVE-2021-21972

CRITICAL · 9.8 CVSS v3.1 Published 2021-02-24
Fix available
A fix is available. Upgrade to 3.10.1.2 / 4.2 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Ransomware High EPSS Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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).

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Critical remote code execution vulnerability in the vSphere Client (HTML5) vCenter Server plugin allows unauthenticated attackers with network access to port 443 to execute commands with unrestricted privileges on the underlying operating system hosting vCenter Server.

MitigationApply VMware patches (vCenter Server 7.0 U1c+, 6.7 U3l+, 6.5 U3n+ or Cloud Foundation 4.2+, 3.10.1.2+); as a temporary measure, restrict network access to port 443.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Cloud FoundationApplication
Affected:>= 3.0, < 3.10.1.2>= 4.0, < 4.2
Vcenter ServerApplication
Affected:= 6.5= 6.7= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if vCenter Server is deployed
    Check the system for vCenter Server components. On the management interface or by checking installed packages: look for 'VMware vCenter Server' or run 'vpxd --version' if you have shell access to the vCenter Appliance.
    Affected if The system is running vCenter Server 6.5, 6.7, or 7.0 (or Cloud Foundation 3.x/4.x)
  2. Determine the exact vCenter Server version
    Access the vSphere Client login page or the Appliance Management Interface (https://[vcenter-fqdn]:5480). The version is displayed on the login page or in the 'About' section. Alternatively, run 'vpxd -v' via SSH to the vCenter Appliance.
    Affected if Version matches 6.5 (any build), 6.7 (any build), or 7.0 (any build before U1c)
  3. Verify the vulnerable vSphere Client plugin is present
    The vulnerability exists in the vCenter Server REST API plugin (vsphere-client-sdk). Confirm by accessing https://[vcenter-fqdn]/api/session and checking if an unauthenticated session can be created (returns a session token without authentication).
    Affected if The /api/session endpoint accepts unauthenticated requests and returns a valid session token
  4. Confirm network exposure on port 443
    Scan the vCenter Server from an external system using 'nmap -p 443 [vcenter-ip]' or check firewall rules to determine if port 443 is accessible from untrusted networks.
    Affected if Port 443 is open to untrusted/unauthenticated network segments

If the system runs an unpatched vCenter Server 6.5, 6.7, or 7.0 with port 443 exposed to the network and the unauthenticated /api/session endpoint is accessible, the environment is affected by CVE-2021-21972.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.10.1.2 / 4.2 or later
Fixed in 3.10.1.24.2
Interim mitigation

Apply VMware patches (vCenter Server 7.0 U1c+, 6.7 U3l+, 6.5 U3n+ or Cloud Foundation 4.2+, 3.10.1.2+); as a temporary measure, restrict network access to port 443.

Recommended fix High confidence

vCenter Server 7.0 U1c+ / 6.7 U3l+ / 6.5 U3n+; Cloud Foundation 4.2+ / 3.10.1.2+

  1. 1. Backup the vCenter Server and underlying database before performing any upgrade.
  2. 2. Review the official VMware security advisory (VMSA-2021-0002) for detailed upgrade instructions.
  3. 3. For vCenter Server 7.x: Upgrade to version 7.0 U1c (build 17327517) or later.
  4. 4. For vCenter Server 6.7: Upgrade to version 6.7 U3l (build 17138064) or later.
  5. 5. For vCenter Server 6.5: Upgrade to version 6.5 U3n (build 16536041) or later.
  6. 6. For Cloud Foundation 4.x: Upgrade to version 4.2 or later.
  7. 7. For Cloud Foundation 3.x: Upgrade to version 3.10.1.2 or later.
  8. 8. After upgrade, verify the vCenter Server services are running correctly.
Caveat Upgrading vCenter Server may require downtime and can impact connected ESXi hosts and virtual machines; ensure compatibility with existing infrastructure before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Cloud Foundation Exploited in the wild — priority engagement
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  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,480
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-21972 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data