CVE-2021-21973

Name: CVE-2021-21973
Creator: NVD / NIST
Published: 2021-02-24T17:15:15.923+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.3/10Actively ExploitedEPSS 88.01%

Last modified Jun 17, 2026

CVE-2021-21973 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue by sending a POST request to vCenter Server plugin leading to information disclosure. CISA has confirmed active exploitation in the wild. EPSS estimates a 88.01% chance of exploitation in the next 30 days.

Description

The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue by sending a POST request to vCenter Server plugin leading to information disclosure. This affects: VMware vCenter Server (7.x before 7.0 U1c, 6.7 before 6.7 U3l and 6.5 before 6.5 U3n) and VMware Cloud Foundation (4.x before 4.2 and 3.x before 3.10.1.2).

Metrics

CVSS 3.1

5.3/10

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

EPSS Probability

88.01%

99.7th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by Mar 21, 2022.

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Vmware	Cloud Foundation	>= 3.0, < 3.10.1.2
Vmware	Cloud Foundation	>= 4.0, < 4.2
Vmware	Vcenter Server	6.5
Vmware	Vcenter Server	6.7
Vmware	Vcenter Server	7.0

References

https://www.vmware.com/security/advisories/VMSA-2021-0002.htmlVendor Advisory
https://www.vmware.com/security/advisories/VMSA-2021-0002.htmlVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21973US Government Resource

Timeline

Published: Feb 24, 2021
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2021-21973?

How severe is CVE-2021-21973?

CVE-2021-21973 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 88.01% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.

How do I fix CVE-2021-21973?

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-2021-21973?

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

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Source: NVD / NIST