CVE-2021-21991

Name: CVE-2021-21991
Creator: NVD / NIST
Published: 2021-09-22T19:15:09.093+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10EPSS 0.31%

Last modified Jun 17, 2026

CVE-2021-21991 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. The vCenter Server contains a local privilege escalation vulnerability due to the way it handles session tokens. A malicious actor with non-administrative user access on vCenter Server host may exploit this issue to escalate privileges to Administrator on the vSphere Client (HTML5) or vCenter Server vSphere Web Client (FLEX/Flash).. EPSS estimates a 0.31% chance of exploitation in the next 30 days.

Description

The vCenter Server contains a local privilege escalation vulnerability due to the way it handles session tokens. A malicious actor with non-administrative user access on vCenter Server host may exploit this issue to escalate privileges to Administrator on the vSphere Client (HTML5) or vCenter Server vSphere Web Client (FLEX/Flash).

Metrics

CVSS 3.1

7.8/10

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

EPSS Probability

0.31%

22.2th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Vmware	Cloud Foundation	>= 3.0, < 3.10.2.2
Vmware	Cloud Foundation	>= 4.0, < 4.3
Vmware	Vcenter Server	6.5
Vmware	Vcenter Server	6.7
Vmware	Vcenter Server	7.0

References

https://www.vmware.com/security/advisories/VMSA-2021-0020.htmlPatch, Vendor Advisory
https://www.vmware.com/security/advisories/VMSA-2021-0020.htmlPatch, Vendor Advisory

Timeline

Published: Sep 22, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21991?

How severe is CVE-2021-21991?

CVE-2021-21991 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.31% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21991?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21991?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST