CVE-2021-20023

CRITICALNVD 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
9.0EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 51%CVSS: 4.9Exploit: cisa kev · ssvc active · kev ransomware · epss top5pct · epss highExposed: 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
96(Act)
EG Risk 96/100SSVC: Act

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: Fix now — active exploitation, automatable, high impact.
EPSS PROB
51%
EPSS %ILE
99%
KEV
⚠ Exploited

Published

April 20, 2021

Last Modified

August 12, 2026

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 63× in last 7d / 257× 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 962 total refreshes for this CVE.

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

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Frequently asked(6)

What is CVE-2021-20023?
CVE-2021-20023 is a critical 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 August 12, 2026. 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

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