NVD / CVE Program· CNA vmware

CVE-2021-21985: The vSphere Client (HTML5) contains a remote code execution vulnerability due to lack of input validation in the Virtual SAN Health Check…

CriticalCVSS 9.8 · v3.1KEVWeaponized No fix recorded

Noroxi assessment

Priority: Now (action score 99/100)

CISA has confirmed exploitation in the wild (Nov 3, 2021); it is known to be used in ransomware campaigns. Remediation deadline for US federal agencies: Nov 17, 2021.
A ready-made attack module is public (Metasploit, Nuclei); exploiting it takes no special expertise.
Probability of exploitation in the next 30 days: 99.9% (FIRST EPSS); higher than 99.9% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
According to the record, no fixed version is available yet.
Mentioned 3 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Patch today or shut off access. Until a fix is released, restrict access to the affected component and follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

The vSphere Client (HTML5) contains a remote code execution vulnerability due to lack of input validation in the Virtual SAN Health Check plug-in which is enabled by default in vCenter Server. A malicious actor with network access to port 443 may exploit this issue to execute commands with unrestricted privileges on the underlying operating system that hosts vCenter Server.

BDU:2021-02848

Published: May 26, 2021
Updated: Aug 12, 2026
EPSS: 99.9% · 99th percentile
CWE: CWE-918

Report tools

JSON

Action score

Now

Patch today or shut off access.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 30 / 30 · Listed
EPSS: 30 / 30 · 99.9%

CISA SSVC decision

Exploitation: active
Automatable: yes
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Nov 3, 2021. That signals real attacks, not theory.

Remediation deadline for US federal agencies: Nov 17, 2021.

Known to be used in ransomware campaigns.

Get told when this record changes

In CISA KEV: exploitation in the wild confirmed
Weaponized exploit exists
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
vmware	vcenter server	cpe:2.3:a:vmware:vcenter_server
vmware	cloud foundation	cpe:2.3:a:vmware:cloud_foundation

Versions reported by the vendor

Affected version ranges reported by the assigning authority (vmware). Independent of NVD's CPE analysis and usually ahead of it.

n/a VMware vCenter Server and VMware Cloud Foundation
- VMware vCenter Server (7.x before 7.0 U2b, 6.7 before 6.7 U3n, 6.5 before 6.5 U3p) and VMware Cloud Foundation (4.x before 4.2.1, 3.x before 3.10.2.1)affected

Affected versions · NVD (5)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

vmware cloud foundation3.0 and later · before 3.10.2.1
vmware cloud foundation4.0 and later · before 4.2.1
vmware vcenter server6.5
vmware vcenter server6.7
vmware vcenter server7.0

Same product

vmware: all records

Other highest-scoring records for the same primary product.

CVE-2023-34048VMware vCenter Server Out-of-Bounds Write VulnerabilityKEV
99Now
CVE-2020-3952Under certain conditions, vmdir that ships with VMware vCenter Server, as part of an embedded or external Platform Services Controller…KEV
96Now
CVE-2026-59310vCenter directory-traversal vulnerabilityKEV
88Now

Published before and after this one in the same product

← EarlierCVE-2019-5537Oct 28, 2019 · Sensitive information disclosure vulnerability resulting from a lack of certificate validation during the File-Based Backup and Restore…
23Monitor
← EarlierCVE-2019-5538Oct 28, 2019 · Sensitive information disclosure vulnerability resulting from a lack of certificate validation during the File-Based Backup and Restore…
23Monitor
Later →CVE-2021-21986May 26, 2021 · The vSphere Client (HTML5) contains a vulnerability in a vSphere authentication mechanism for the Virtual SAN Health Check, Site Recovery…
43Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

Metasploit module ×1
Nuclei detection template ×1
Proof-of-concept repository on GitHub ×10

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
Source	Kind	Date
Proof-of-concept repository on GitHub	10 repositories	2021-05-27 → 2021-11-09
Metasploit module	exploit/linux/http/vmware_vcenter_vsan_health_rceVMware vCenter Server Virtual SAN Health Check Plugin RCEexploit	2021-05-25
Nuclei detection template	Nuclei template CVE-2021-21985	—

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.