---
title: "vCenter plugin RCE (CVE-2021-21972)"
canonical: https://trickest.com/library/cve-2021-21972-vcenter-vsphere-client-plugin-rce
description: "Flag VMware vCenter hosts for CVE-2021-21972 by reading version and build from GET /sdk. Floors 6.5 U3n / 6.7 U3l / 7.0 U1c. No plugin upload."
---

# vCenter plugin RCE (CVE-2021-21972)

## Overview

This workflow finds VMware vCenter Server and sorts each host by whether its version and build fall below the CVE-2021-21972 floors in the graph. CVE-2021-21972 is remote code execution in the vSphere Client (HTML5) through a plugin upload path. This check never hits a plugin URL and never uploads a file. Give it hostnames, IP addresses, or URLs you are authorised to test. The workflow GETs `/sdk` only, fingerprints vCenter from markers in that response, parses the `VMware vCenter Server` version and `build-` number, and compares the tuple to the 6.5 U3n, 6.7 U3l, and 7.0 U1c floors. Every host comes back affected or not, so a fleet advisory becomes an evidenced list for [exposure management](/use-cases/exposure-management). There is no plugin file-upload and no confirm step.

Run it on a schedule when management planes change. A rebuilt VCSA that landed on an older 6.7 build is the reason the same fingerprint stays useful.

## Pipeline

1. Read the target list. Hosts, URLs, or ranges, one per line, become the scope.
2. GET `/sdk` on each host and fingerprint vCenter from response markers such as `VMware vCenter Server`, `vim.ServiceInstance`, and `build-`.
3. Parse the version and build string and compare the tuple to the CVE-2021-21972 floors in the graph (6.5 U3n, 6.7 U3l, 7.0 U1c).
4. Collect the per-host rows: product match, version, vulnerable flag, and any fetch error.
5. Emit the summary counts: hosts checked, product hits, vulnerable, and errors.

## Inputs

- **Target scope.** Hostnames, IP addresses, CIDR ranges, or URLs, one per line. Full URLs and host:port entries work too, since the workflow normalizes each into a bare host. Point it at scope you are authorised to test.

## Outputs

- **results.jsonl.** One row per host: URL, whether vCenter was detected, the version read, the vulnerable flag, and detail text.
- **findings.jsonl.** The same per-host verdict shaped for triage, with severity set from the vulnerable flag.
- **summary.json.** Counts across the list: targets, product hits, vulnerable, and errors, plus the detection notes from the graph.

## Integrations

- HTTP. Unauthenticated GET of `/sdk` only. No plugin upload and no vsphere-client file write.

## Sample output

The records below are illustrative and do not come from a real run. They show one vCenter host below a CVE-2021-21972 floor, one at or above its branch floor, and one host that is not the product.

```jsonl
{"url": "https://vc.example.com", "is_product": true, "product_version": "7.0.1.00000000", "vulnerable": true, "detail": "below 7.0 U1c floor"}
{"url": "https://vc.example.org", "is_product": true, "product_version": "7.0.1.17327517", "vulnerable": false, "detail": "at or above fixed release"}
{"url": "https://shop.example.net", "is_product": false, "product_version": null, "vulnerable": false, "detail": "not identified as VMware vCenter Server"}
```

```json
{"cve": "CVE-2021-21972", "total_targets": 3, "product_detected": 2, "vulnerable": 1, "errors": 0}
```

## FAQ

### Which vCenter versions does this flag?

Hosts whose parsed version and build tuple fall below the floors in the graph: 6.5 U3n, 6.7 U3l, and 7.0 U1c. The compare uses the string the `/sdk` response itself served.

### Does an affected row mean the plugin upload worked?

No. The check only GETs `/sdk` and reads version and build. It does not hit a plugin endpoint and it does not confirm RCE.

### Is this check safe on production?

Yes. It is a read-only unauthenticated GET of `/sdk`. It does not log in or upload a file.

### Does the check need credentials?

No. It fingerprints the public `/sdk` surface the way an external scanner would.

### What is CVE-2021-21972?

Remote code execution in the VMware vSphere Client (HTML5) through a plugin upload path on vCenter Server. This workflow maps hosts to that CVE by version and build exposure only.

## Related workflows

- [VMware vCenter plugin SSRF (CVE-2021-21973)](/library/cve-2021-21973-vcenter-plugin-ssrf). Reach for it when you need the companion plugin SSRF fingerprint on the same fleet.
- [vCenter Info Disclosure (CVE-2022-22948)](/library/vmware-vcenter-server-info-disclosure-cve-2022-22948). Reach for it when you need the later vCenter information disclosure check.

---
_Markdown source of https://trickest.com/library/cve-2021-21972-vcenter-vsphere-client-plugin-rce._