CVE-2021-21973: in the CISA KEV catalogue
VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability. CISA added CVE-2021-21973 to the Known Exploited Vulnerabilities catalogue on 2022-03-07 with a default due date of 2022-03-21. Known ransomware campaign use: Unknown. Forensic triage flag: No.
VMware vCenter Server and Cloud Foundation Server contain a SSRF vulnerability due to improper validation of URLs in a vCenter Server plugin. This allows for information disclosure. (CISA description)
- Vendor / product
- VMware vCenter Server and Cloud Foundation
- CWE
- CWE-20, CWE-918
- CISA required action
- Apply updates per vendor instructions.
- EPSS
- 88%, percentile 99 (scored 2026-11-03)
EPSS puts about 88 in 100 odds (88%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 99% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2021-21973 in the CISA KEV catalogue?
Yes. CISA added CVE-2021-21973 (VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2022-03-07. CISA's default due date for it is 2022-03-21.
Is CVE-2021-21973 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2021-21973. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2021-21973?
CISA's required action: Apply updates per vendor instructions.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2021-21973