CVE-2021-37334

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 2.7%, top 15% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 3%CVSS: 9.8Exploit: None knownExposed: 0

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

Umbraco Forms version 4.0.0 up to and including 8.7.5 and below are vulnerable to a security flaw that could lead to a remote code execution attack and/or arbitrary file deletion. A vulnerability occurs because validation of the file extension is performed after the file has been stored in a temporary directory. By default, files are stored within the application directory structure at %BASEDIR%/APP_DATA/TEMP/FileUploads/. Whilst access to this directory is restricted by the root web.config file, it is possible to override this restriction by uploading another specially crafted web.config file to the temporary directory. It is possible to exploit this flaw to upload a malicious script file to execute arbitrary code and system commands on the server.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
50(Track)
EG Risk 50/100SSVC: Track

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
Severity98% × 45%
Exploitation3% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
3%
EPSS %ILE
85%
KEV
Not listed

Published

August 25, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated Sep 4, 2026
⚠️ Active exploitation confirmed. No patch confirmed yet.
generic🔴 Active Exploitation

Security advisory: Security patch ready on July 20th, 2021

https://umbraco.com/blog/security-advisory-security-patches-for-umbraco-forms-ready-on-july-20th-2021-at-7-am-utc/
generic

Security Advisory 20th of July, 2021: Patch is now available

https://umbraco.com/blog/security-advisory-20th-of-july-2021-patch-is-now-available/

Data Freshness Timeline

(refreshed 8× in last 7d / 31× 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 149 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2021-37334?
CVE-2021-37334 is a critical vulnerability published on August 25, 2021. Umbraco Forms version 4.0.0 up to and including 8.7.5 and below are vulnerable to a security flaw that could lead to a remote code execution attack and/or arbitrary file deletion. A vulnerability occurs because validation of the file extension is performed after the file has been stored in a…
When was CVE-2021-37334 disclosed?
CVE-2021-37334 was first published in the National Vulnerability Database on August 25, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-37334 actively exploited?
CVE-2021-37334 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3% probability of exploitation in the next 30 days, which ranks it in the top 14.8% of all scored CVEs.
What is the CVSS score of CVE-2021-37334?
CVE-2021-37334 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-37334?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-37334, 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-2021-37334

Explore →

Is Your Infrastructure Affected by CVE-2021-37334?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs