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Cloud FoundationApplication · VMware

CVE-2021-21992

MEDIUM · 6.5 CVSS v3.1 Published 2021-09-22
Fix available
A fix is available. Upgrade to 3.10.2.2 / 4.3 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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 vCenter Server contains a denial-of-service vulnerability due to improper XML entity parsing. A malicious actor with non-administrative user access to the vCenter Server vSphere Client (HTML5) or vCenter Server vSphere Web Client (FLEX/Flash) may exploit this issue to create a denial-of-service condition on the vCenter Server host.

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 · moderate confidence

The vCenter Server contains a denial-of-service vulnerability stemming from improper XML entity parsing. A malicious actor with non-administrative user access to either the vSphere Client (HTML5) or vSphere Web Client (FLEX/Flash) can exploit this XXE-type vulnerability to trigger excessive resource consumption or crashes, resulting in denial of service on the vCenter Server.

MitigationApply the official VMware security patch for CVE-2021-21992, which addresses the improper XML entity parsing in vCenter Server. Ensure the patch is tested in a non-production environment before deploying to production, and schedule appropriate maintenance windows given vCenter Server criticality.

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, < 3.10.2.2>= 4.0, < 4.3
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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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. Check vCenter Server installed version
    Log into the vSphere Client, navigate to Administration > System Configuration > vCenter Server > About, or run 'vpxd -v' from the vCenter Server Appliance shell. Alternatively, access the Managed Object Browser at https://<vcenter>/mob and navigate to ServiceInstance > content > about.
    Affected if The displayed version matches 6.5.x, 6.7.x, or 7.0.x (any minor version). Cloud Foundation versions 3.0 to 3.10.2.1 or 4.0 to 4.2 are also affected.
  2. Verify vSphere Client (HTML5) service status
    From the vCenter Server Appliance shell, run 'service-control --status vsphere-ui' or check the 'vsphere-ui' service status in the vCenter Server Appliance Management Interface (VAMI) at port 5480.
    Affected if The service is running and accessible on port 443/9443, as this exposes the vulnerable HTML5 client interface.
  3. Verify vSphere Web Client (FLEX) service status
    From the vCenter Server Appliance shell, run 'service-control --status vsphere-webclient' or check the 'vsphere-webclient' service status in VAMI at port 5480.
    Affected if The service is running and accessible, as this exposes the vulnerable Flash-based client interface where the XXE flaw exists.
  4. Confirm vCenter Server is directly internet-facing or accessible to untrusted users
    Review firewall rules, VPN configurations, and access control lists to determine if the vCenter Server management interfaces (ports 443, 9443) are exposed to networks with untrusted users. Use 'grep -i 'accept' /etc/vmware/firewall/service.xml' or check firewall configuration in the vSphere Client under Networking > Firewall rules.
    Affected if The vSphere Client or Web Client interfaces are accessible from networks where non-administrative users exist who could trigger the XXE vulnerability.

You are affected if your vCenter Server version is 6.5, 6.7, or 7.0 (any patch level) or Cloud Foundation 3.0-3.10.2.1 or 4.0-4.2, and the vSphere Client or Web Client services are running and accessible to the users in question.

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 3.10.2.2 / 4.3 or later
Fixed in 3.10.2.24.3
Interim mitigation

Apply the official VMware security patch for CVE-2021-21992, which addresses the improper XML entity parsing in vCenter Server. Ensure the patch is tested in a non-production environment before deploying to production, and schedule appropriate maintenance windows given vCenter Server criticality.

Recommended fix High confidence

vCenter Server: 6.5/6.7 to 6.7 U3o or 7.0 U3h; 7.0 to 7.0 U3h | Cloud Foundation: 3.x to 3.10.2.2+; 4.x to 4.3+

  1. 1. Identify your current vCenter Server or Cloud Foundation version from the vSphere Client under 'System Information'.
  2. 2. For vCenter Server 6.5: Upgrade to vCenter Server 6.7 U3o or later, or upgrade to 7.0 U3h or later.
  3. 3. For vCenter Server 6.7: Upgrade to vCenter Server 6.7 U3o or later, or upgrade to 7.0 U3h or later.
  4. 4. For vCenter Server 7.0: Upgrade to vCenter Server 7.0 U3h or later.
  5. 5. For Cloud Foundation 3.x: Upgrade to version 3.10.2.2 or later.
  6. 6. For Cloud Foundation 4.x: Upgrade to version 4.3 or later.
  7. 7. Schedule maintenance window and ensure backups exist before performing upgrade.
  8. 8. Follow VMware documentation for upgrading vCenter Server or apply VMware security patch for CVE-2021-21992.
Caveat Review VMware Release Notes for upgrade prerequisites and potential compatibility considerations before upgrading

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

Fix this in Cloud Foundation Scoped from the published advisory
  • Consultation4.0 h
  • 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-2021-21992 in production — separate from our analysis above.

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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
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  • 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