# CVE-2021-21973: VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability

- Exploited (CISA KEV): yes, added 2022-03-07
- Published: 2021-02-24
- CVSS: 5.3 MEDIUM (v3.1)
- EPSS: 88.0% (100th percentile)
- CWE: CWE-20, CWE-918

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).

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Before feed history | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | Before feed history | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2023-08-08 | — |
| Akamai | No public source | — | — |
| OWASP CRS | Before feed history | — | — |

### F5

- 2023-08-08 · updated · rule 200014017
  > Updated: signature 200014017 "VMware vCenter vcIP SSRF" (Abuse of Functionality, risk High), systems: Microsoft Windows, Java Servlets/JSP. References: CVE-2021-21973.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog
- 2023-09-12 · updated · rule 200014017
  > Updated: signature 200014017 "VMware vCenter vcIP SSRF" (Abuse of Functionality, risk High), systems: Microsoft Windows, Java Servlets/JSP. References: CVE-2021-21973.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: passed (0 of 1 requests blocked), template CVE-2021-21973, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: passed (0 of 1 requests blocked), template CVE-2021-21973, 2026-11-02

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2021-21973 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2021-21973