CVE-2021-21973

CRITICALNVD 5.39.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2022-03-07), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 5.3 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 4 sources updated this weekExploited in the wild
9.0EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 88%CVSS: 5.3Exploit: cisa kev · ssvc active · epss top5pct · epss high · public exploitExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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).

CVSS v3
5.3
EG Score
9.0(high)
EG Risk
96(Attend)
EG Risk 96/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity90% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
88%
EPSS %ILE
100%
KEV
⚠ Exploited

Published

February 24, 2021

Last Modified

October 30, 2025

Advisory Details (2)

Auto-updated Jun 13, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21973
generic

Support Content Notification - Support Portal - Broadcom support portal

https://www.vmware.com/security/advisories/VMSA-2021-0002.html

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 53× in last 7d / 228× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 787 total refreshes for this CVE.

  1. 2026-09-19 23:18 UTCGHSA enrichment
  2. 2026-09-19 19:18 UTCGHSA enrichment
  3. 2026-09-19 15:17 UTCGHSA enrichment
  4. 2026-09-19 11:16 UTCGHSA enrichment
  5. 2026-09-19 07:16 UTCGHSA enrichment
  6. 2026-09-19 03:16 UTCGHSA enrichment
  7. 2026-09-18 23:15 UTCGHSA enrichment
  8. 2026-09-18 19:20 UTCCISA KEV update
  9. 2026-09-18 19:15 UTCGHSA enrichment
  10. 2026-09-18 15:15 UTCGHSA enrichment
  11. 2026-09-18 14:15 UTCCISA KEV update
  12. 2026-09-18 11:14 UTCGHSA enrichment
  13. 2026-09-18 07:14 UTCGHSA enrichment
  14. 2026-09-18 03:14 UTCGHSA enrichment
  15. 2026-09-17 23:13 UTCGHSA enrichment
  16. 2026-09-17 19:13 UTCGHSA enrichment
  17. 2026-09-17 15:12 UTCGHSA enrichment
  18. 2026-09-17 11:12 UTCGHSA enrichment
  19. 2026-09-17 07:11 UTCGHSA enrichment
  20. 2026-09-17 03:11 UTCGHSA enrichment
  21. 2026-09-16 23:10 UTCGHSA enrichment
  22. 2026-09-16 19:09 UTCGHSA enrichment
  23. 2026-09-16 15:09 UTCEG score recompute
  24. 2026-09-16 15:09 UTCGHSA enrichment
  25. 2026-09-16 14:10 UTCCISA KEV update
Show 75 more
  1. 2026-09-16 14:05 UTCEPSS rescore
  2. 2026-09-16 14:04 UTCEPSS rescore
  3. 2026-09-16 11:08 UTCGHSA enrichment
  4. 2026-09-16 07:08 UTCGHSA enrichment
  5. 2026-09-16 03:08 UTCGHSA enrichment
  6. 2026-09-15 23:07 UTCGHSA enrichment
  7. 2026-09-15 19:05 UTCGHSA enrichment
  8. 2026-09-15 15:04 UTCGHSA enrichment
  9. 2026-09-15 11:03 UTCGHSA enrichment
  10. 2026-09-15 07:03 UTCEG score recompute
  11. 2026-09-15 07:03 UTCGHSA enrichment
  12. 2026-09-15 03:06 UTCEPSS rescore
  13. 2026-09-15 03:02 UTCGHSA enrichment
  14. 2026-09-14 23:02 UTCGHSA enrichment
  15. 2026-09-14 19:24 UTCCISA KEV update
  16. 2026-09-14 19:01 UTCGHSA enrichment
  17. 2026-09-14 15:00 UTCGHSA enrichment
  18. 2026-09-14 11:00 UTCGHSA enrichment
  19. 2026-09-14 07:00 UTCGHSA enrichment
  20. 2026-09-14 03:00 UTCGHSA enrichment
  21. 2026-09-13 23:00 UTCGHSA enrichment
  22. 2026-09-13 19:00 UTCEG score recompute
  23. 2026-09-13 19:00 UTCGHSA enrichment
  24. 2026-09-13 16:43 UTCEPSS rescore
  25. 2026-09-13 15:00 UTCGHSA enrichment
  26. 2026-09-13 11:00 UTCGHSA enrichment
  27. 2026-09-13 06:59 UTCGHSA enrichment
  28. 2026-09-13 03:00 UTCGHSA enrichment
  29. 2026-09-12 22:59 UTCGHSA enrichment
  30. 2026-09-12 18:59 UTCGHSA enrichment
  31. 2026-09-12 14:59 UTCEG score recompute
  32. 2026-09-12 14:59 UTCGHSA enrichment
  33. 2026-09-12 14:57 UTCEPSS rescore
  34. 2026-09-12 10:58 UTCGHSA enrichment
  35. 2026-09-12 06:56 UTCGHSA enrichment
  36. 2026-09-12 02:55 UTCGHSA enrichment
  37. 2026-09-11 22:54 UTCGHSA enrichment
  38. 2026-09-11 18:54 UTCGHSA enrichment
  39. 2026-09-11 18:49 UTCCISA KEV update
  40. 2026-09-11 14:49 UTCGHSA enrichment
  41. 2026-09-11 10:48 UTCGHSA enrichment
  42. 2026-09-11 06:46 UTCGHSA enrichment
  43. 2026-09-11 02:46 UTCGHSA enrichment
  44. 2026-09-10 22:46 UTCGHSA enrichment
  45. 2026-09-10 19:28 UTCCISA KEV update
  46. 2026-09-10 18:46 UTCGHSA enrichment
  47. 2026-09-10 14:46 UTCGHSA enrichment
  48. 2026-09-10 10:46 UTCEG score recompute
  49. 2026-09-10 10:45 UTCGHSA enrichment
  50. 2026-09-10 09:29 UTCEPSS rescore
  51. 2026-09-10 06:43 UTCGHSA enrichment
  52. 2026-09-10 02:42 UTCGHSA enrichment
  53. 2026-09-09 22:42 UTCGHSA enrichment
  54. 2026-09-09 19:08 UTCCISA KEV update
  55. 2026-09-09 18:40 UTCGHSA enrichment
  56. 2026-09-09 14:40 UTCGHSA enrichment
  57. 2026-09-09 10:40 UTCGHSA enrichment
  58. 2026-09-09 06:39 UTCGHSA enrichment
  59. 2026-09-09 02:38 UTCGHSA enrichment
  60. 2026-09-08 22:38 UTCGHSA enrichment
  61. 2026-09-08 18:54 UTCCISA KEV update
  62. 2026-09-08 18:33 UTCGHSA enrichment
  63. 2026-09-08 14:30 UTCGHSA enrichment
  64. 2026-09-08 10:27 UTCGHSA enrichment
  65. 2026-09-08 06:26 UTCGHSA enrichment
  66. 2026-09-08 02:25 UTCGHSA enrichment
  67. 2026-09-07 22:25 UTCGHSA enrichment
  68. 2026-09-07 18:24 UTCGHSA enrichment
  69. 2026-09-07 14:24 UTCGHSA enrichment
  70. 2026-09-07 10:23 UTCGHSA enrichment
  71. 2026-09-07 06:21 UTCGHSA enrichment
  72. 2026-09-07 02:19 UTCGHSA enrichment
  73. 2026-09-06 22:15 UTCGHSA enrichment
  74. 2026-09-06 18:15 UTCGHSA enrichment
  75. 2026-09-06 14:14 UTCEG score recompute

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2021/CVE-2021-21973.yaml
    First seen Jan 1, 2021

    VMware vSphere - Server-Side Request Forgery

    Open source ↗

Frequently asked(6)

What is CVE-2021-21973?
CVE-2021-21973 is a critical vulnerability published on February 24, 2021. 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…
When was CVE-2021-21973 disclosed?
CVE-2021-21973 was first published in the National Vulnerability Database on February 24, 2021, with the most recent update on October 30, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-21973 actively exploited?
Yes. CISA added CVE-2021-21973 to the Known Exploited Vulnerabilities catalog on March 7, 2022, affecting VMware vCenter Server and Cloud Foundation. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-21973?
CVE-2021-21973 has a CVSS v3 base score of 5.3 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2021-21973?
CVE-2021-21973 affects VMware vCenter Server and Cloud Foundation. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2021-21973?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21973, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2021-21973

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