Exploited CVEs / VMware / CVE-2021-21973

CVE-2021-21973

VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2022-03-21 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Broadcom (VMware) Security Advisories, linked below.

Risk summary

MediumCISA KEV

5.3

CVSS v3 base

88%

EPSS exploit probability

Medium

Severity

2022-03-07

Added to KEV

2022-03-21 (past due)

CISA due date

Actively exploited VMware vCenter Server and Cloud Foundation vulnerability, Medium severity, CVSS v3 5.3. Added to the CISA KEV catalog 2022-03-07.

Senserva AI read on CVE-2021-21973 CISA required action Official fix for CVE-2021-21973 Admin questions

Senserva AI Opinion for CVE-2021-21973

An SSRF flaw in a vCenter Server plugin lets attackers make the server issue requests on their behalf, disclosing information useful for mapping the virtualization environment. The CVSS score is only 5.3, Medium Severity, yet the 88% EPSS probability and KEV listing show attackers use it in practice, usually as reconnaissance ahead of more damaging vCenter attacks. vCenter's position managing the hypervisor estate means even information leaks matter.

Do this: Confirm vCenter is patched and unreachable from the internet, restricting management-plane access to a dedicated admin network.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2021-21973

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2021-21973, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2021-21973.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2021-21973: VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability
- Affected: VMware vCenter Server and Cloud Foundation
- Severity: Medium, CVSS v3 5.3; EPSS 30-day exploitation probability 88%
- Added to CISA KEV: 2022-03-07; federal remediation due 2022-03-21
- Ransomware-linked: no
- CISA required action: Apply updates per vendor instructions.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch now

Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.

The fix ships from the vendor: Broadcom (VMware) Security Advisories.

Do this now: Federal remediation deadline 2022-03-21; treat it as your outer bound. Patch now and verify deployment on every exposed device.

Updated August 29, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2021-21973

Published: 2022-03-07
Last revised: 2022-03-07
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

2022-03-07 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 5.3; EPSS first scored at 88.0%
2026-08-12 EPSS 88.0% to 87.6%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2022-03-21 (past due).

Apply updates per vendor instructions.

Official fix for CVE-2021-21973

The authoritative fix and affected-version list are published by the vendor. Find the vCenter Server and Cloud Foundation advisory on Broadcom (VMware) Security Advisories.

Broadcom (VMware) Security Advisories CISA KEV entry

Common questions about CVE-2021-21973

Is CVE-2021-21973 actively exploited?

Yes. CVE-2021-21973 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2022-03-07, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 88%.

What is the CISA deadline and required action for CVE-2021-21973?

CISA set the federal (BOD 22-01) remediation due date at 2022-03-21, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.

What fixes CVE-2021-21973?

The authoritative fix is in the vendor advisory: see Broadcom (VMware) Security Advisories for the patched vCenter Server and Cloud Foundation versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2021-21973?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2021-21973's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

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All VMware exploited CVEs on one page: VMware vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.