---
id: "CVE-2021-21973"
kind: "vulnerability"
aliases: ["CVE-2021-21973"]
title: "VMware vCenter Server and Cloud Foundation: VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability"
severity: "medium"
cvss: 5.3
epss: 0.88012
exploited: true
status: "open"
category: "vendor"
products: [{"name": "VMware vCenter Server and Cloud Foundation", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["cloud-foundation", "exploited", "vcenter", "vendor", "vmware"]
not_affected_if: ["unpatched-versions-not-in-use"]
published_at: "2021-02-24T17:15:15+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-21973", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-21973", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-21973", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# VMware vCenter Server and Cloud Foundation: VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability

VMware vCenter Server and Cloud Foundation contain a server-side request forgery flaw caused by improper URL validation in a vCenter plugin. An attacker can make the server send requests to internal hosts and read back the responses, which discloses information.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:VMware vCenter Server and Cloud Foundation affected ? fixed ?

## How to check

Check the installed vCenter Server version against the VMware advisory for CVE-2021-21973 (VMSA-2021-0002).

## Fix

Apply the VMware update for vCenter Server and Cloud Foundation per vendor instructions (CISA required action).

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-21973
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-21973
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-21973

## From the sources

The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue by sending a POST request to vCenter Server plugin leading to information disclosure. 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).

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_