How severe is CVE-2021-21986?

CVE-2021-21986 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-21986 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 13% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21986?

CVE-2021-21986 primarily affects Vmware Vcenter Server. In total, 52 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-21986?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-21986 published?

CVE-2021-21986 was published on 2021-05-26 and last updated on 2026-06-17.

CVE-2021-21986

CVE-2021-21986 is a critical-severity vulnerability in Vmware Vcenter Server with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 13% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-306.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 13% (96th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-306
Affected product: Vmware Vcenter Server
Published: 2021-05-26
Last modified: 2026-06-17

Description

The vSphere Client (HTML5) contains a vulnerability in a vSphere authentication mechanism for the Virtual SAN Health Check, Site Recovery, vSphere Lifecycle Manager, and VMware Cloud Director Availability plug-ins. A malicious actor with network access to port 443 on vCenter Server may perform actions allowed by the impacted plug-ins without authentication.

Frequently asked questions

What is CVE-2021-21986?: The vSphere Client (HTML5) contains a vulnerability in a vSphere authentication mechanism for the Virtual SAN Health Check, Site Recovery, vSphere Lifecycle Manager, and VMware Cloud Director Availability plug-ins. A malicious actor with network access to port 443 on vCenter Server may perform actions allowed by the impacted plug-ins without authentication.
How severe is CVE-2021-21986?: CVE-2021-21986 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-21986 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 13% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21986?: CVE-2021-21986 primarily affects Vmware Vcenter Server. In total, 52 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-21986?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-21986 published?: CVE-2021-21986 was published on 2021-05-26 and last updated on 2026-06-17.

References

Affected products (52)

cpe:2.3:a:vmware:vcenter_server:6.5:-:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:a:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:b:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:c:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:d:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:e:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:f:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update1:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update1b:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update1c:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update1d:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update1e:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update1g:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update2:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update2b:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update2c:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update2d:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update2g:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update3:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update3d:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update3f:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update3k:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.5:update3n:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:-:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:a:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:b:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:d:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update1:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update1b:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update2:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update2a:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update2c:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3a:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3b:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3f:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3g:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3j:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3l:*:*:*:*:*:*
cpe:2.3:a:vmware:vcenter_server:6.7:update3m:*:*:*:*:*:*

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