CVE-2021-20023

MEDIUMNVD 4.99.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 4.9 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
4.9
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS: 50%CVSS: 4.9Exploit: NoneExposed: 0

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

SonicWall Email Security version 10.0.9.x contains a vulnerability that allows a post-authenticated attacker to read an arbitrary file on the remote host.

CVSS v3
4.9
EG Score
9.0(high)
EG Risk
81(Attend)
EG Risk 81/100SSVC: 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%
Automatability0% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS
98.8%
KEV
⚠ Exploited

Published

April 20, 2021

Last Modified

November 12, 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-2021-20023
generic

Security Advisory

https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0010

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 43× in last 7d / 223× 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 441 total refreshes for this CVE.

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

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Frequently asked(6)

What is CVE-2021-20023?
CVE-2021-20023 is a medium vulnerability published on April 20, 2021. SonicWall Email Security version 10.0.9.x contains a vulnerability that allows a post-authenticated attacker to read an arbitrary file on the remote host.
When was CVE-2021-20023 disclosed?
CVE-2021-20023 was first published in the National Vulnerability Database on April 20, 2021, with the most recent update on November 12, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-20023 actively exploited?
Yes. CISA added CVE-2021-20023 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting SonicWall SonicWall Email Security. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-20023?
CVE-2021-20023 has a CVSS v3 base score of 4.9 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2021-20023?
CVE-2021-20023 affects SonicWall SonicWall Email Security. 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-2021-20023?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-20023, 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-2021-20023

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