CVE-2021-21973: VMware vCenter Server and Cloud Foundation Server Side Request Forgery (SSRF) Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , 376 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 88%
EPSS score, percentile 99.8 of all scored records
- How severe?
- 5.3 Medium
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
CISA deadline . Apply updates per vendor instructions.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- 7.x before 7.0 U1c
- 6.7 before 6.7 U3l
- 6.5 before 6.5 U3n
- 4.x before 4.2
- 3.x before 3.10.1.2
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: .
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 7.x before 7.0 U1c |
| Affected | 6.7 before 6.7 U3l |
| Affected | 6.5 before 6.5 U3n |
| Status | Versions |
|---|---|
| Affected | 4.x before 4.2 |
| Affected | 3.x before 3.10.1.2 |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
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.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2021-21973 to its Known Exploited Vulnerabilities (KEV) catalog on 7 Mar 2022.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 21 Mar 2022.
- The CVE record was published on 24 Feb 2021, 376 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 5.3 (Medium), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 88% (percentile 99.8), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
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).
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CISA due date for the required action | |
| CVE record last updated |
References
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