CVE-2021-20042

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2021-12-09. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 3%CVSS: 9.8Exploit: NoneExposed: 0

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

An unauthenticated remote attacker can use SMA 100 as an unintended proxy or intermediary undetectable proxy to bypass firewall rules. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
84.0%
KEV
Not listed

Published

December 8, 2021

Last Modified

November 21, 2024

Advisory Details (1)

Auto-updated Jun 22, 2026
No patch confirmed yet.
generic

Security Advisory

https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0026

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 47× 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.

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

Frequently asked(5)

What is CVE-2021-20042?
CVE-2021-20042 is a critical vulnerability published on December 8, 2021. An unauthenticated remote attacker can use SMA 100 as an unintended proxy or intermediary undetectable proxy to bypass firewall rules. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances.
When was CVE-2021-20042 disclosed?
CVE-2021-20042 was first published in the National Vulnerability Database on December 8, 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-2021-20042 actively exploited?
CVE-2021-20042 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 84.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-20042?
CVE-2021-20042 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-20042?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-20042, 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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