Threats / VMware / CVE-2021-21985
CVE-2021-21985
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-16
VMware vCenter Server vulnerability
VMware vCenter Server contains an improper input validation vulnerability in the Virtual SAN Health Check plug-in that enables remote code execution on affected systems.
Verdict
Today item, not a backlog item.
This vulnerability allows unauthenticated remote attackers to execute arbitrary code on vCenter Server instances. The flaw resides in insufficient input validation within a default-enabled component, creating a direct path to system compromise without requiring valid credentials.
CISA KEV Yes · 2021-11-033Ransomware use Flagged3EPSS 0.99999 (verify live)4Exploit Weaponized · public PoC5
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
742 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 2021-11-03), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.99999 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: VMware, vCenter Server. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-20 Improper Input Validation, CWE-470 Unsafe Reflection, CWE-918 Server-Side Request Forgery (SSRF) — weakness family: Injection.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No threat-actor attribution is established from the public feed 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 targeting the Virtual SAN Health Check plug-in's input validation weakness.
Business
Attackers gain initial access to the vCenter infrastructure without authentication, bypassing perimeter controls.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I inject code through the unvalidated input parameter to achieve remote code execution on the vCenter Server.
Business
The attacker establishes command execution capability within the virtualization management layer, gaining control over the entire infrastructure.
3
Lateral reach — past segmentation narrative 3
Attacker
I use this foothold to deploy ransomware or establish persistent access across the virtualized environment.
Business
Critical business operations dependent on virtualized systems face encryption, data exfiltration, or extended downtime affecting revenue and operations.
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 named in the public CVE record — the work behind this find is unattributed.