Threats / VMware / CVE-2021-21973
CVE-2021-21973
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
VMware vCenter Server and Cloud Foundation vulnerability
VMware vCenter Server and Cloud Foundation contain a server-side request forgery vulnerability in a plugin that improperly validates URLs, enabling information disclosure.
Verdict
Today item — known-exploited.
A SSRF flaw in vCenter Server and Cloud Foundation plugins allows unauthenticated attackers to bypass URL validation and access internal resources, leading to sensitive information exposure. Active exploitation in the wild increases risk.
CISA KEV Yes · 2022-03-074EPSS 0.8764 (verify live)5Exploit Weaponized · public PoC6CVSS 5.3 (CISA)3CISA SSVC Exploitation: active · Automatable: yes · Impact: partial3
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
5 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-07).
Probability (EPSS)
EPSS 0.8764 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) · Affected: VMware, vCenter Server and Cloud Foundation. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-20 Improper Input Validation, CWE-918 Server-Side Request Forgery (SSRF).CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 376 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious request to the vulnerable plugin that bypasses URL validation to access internal resources.
Business
Confidential infrastructure details, credentials, and internal service configurations are exposed to unauthorized parties.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the SSRF to probe and enumerate internal network services and cloud infrastructure endpoints.
Business
Attack surface mapping enables adversaries to identify and target additional systems within the environment.
3
Lateral reach — past segmentation narrative 3
Attacker
I leverage disclosed internal information to pivot toward higher-value targets or escalate privileges within the infrastructure.
Business
Compromised vCenter environments can lead to widespread virtualization platform compromise and lateral movement across hosted systems.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by vmwareCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
npub1j7gt9ky7sfcrjn8jjee6693dkzvk4rahs0fk2suu7968dfns62zs3mqm3y.