CVE-2021-21985Known exploitationPublic exploitNetwork attack vector

Unauthenticated code execution via unsafe Java reflection

Published May 26, 2021 · Updated Aug 12, 2026

Remote code execution in VMware vCenter Server and Cloud Foundation allows remote attackers to run privileged commands through port 443. The Virtual SAN Health Check plug-in's ProxygenController accepts attacker-chosen class and method names, then invokes them through unsafe Java reflection. The plug-in is enabled by default, so unauthenticated network access to the vSphere Client HTTPS service is enough to execute code with unrestricted host privileges.

CVSS severity9.8
Critical
EPSS probability100.00%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in VMware vCenter Server and Cloud Foundation allows remote attackers to run privileged commands through port 443. The Virtual SAN Health Check plug-in's ProxygenController accepts attacker-chosen class and method names, then invokes them through unsafe Java reflection. The plug-in is enabled by default, so unauthenticated network access to the vSphere Client HTTPS service is enough to execute code with unrestricted host privileges.

The record

CVE
CVE-2021-21985
Published
May 26, 2021
Updated
Aug 12, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-470, CWE-20, CWE-918, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8CISACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsShadowserver observations through Sep 16, 2026. Gaps indicate unavailable data.
Sep 10, 2026Sep 16, 2026
View daily counts
Reporting dayUnique IPs
Sep 10, 2026Unavailable
Sep 11, 2026Unavailable
Sep 12, 2026Unavailable
Sep 13, 2026Unavailable
Sep 14, 20262
Sep 15, 2026Unavailable
Sep 16, 20262
Latest reporting daySep 16, 2026
Latest daily unique IPs2
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-470Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
CWE-20Improper Input Validation
CWE-918Server-Side Request Forgery (SSRF)
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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