CVE-2023-33009

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2023-06-05), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 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
9.8EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 28%CVSS: 9.8Exploit: cisa kev · ssvc active · epss top5pctExposed: 0

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

A buffer overflow vulnerability in the notification function in Zyxel ATP series firmware versions 4.60 through 5.36 Patch 1, USG FLEX series firmware versions 4.60 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.60 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.60 through 5.36 Patch 1, VPN series firmware versions 4.60 through 5.36 Patch 1, ZyWALL/USG series firmware versions 4.60 through 4.73 Patch 1, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device.

CVSS v3
9.8
EG Score
9.8(high)
EG Risk
99(Act)
EG Risk 99/100SSVC: 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
Severity98% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Fix now — active exploitation, automatable, high impact.
EPSS PROB
28%
EPSS %ILE
98%
KEV
⚠ Exploited

Published

May 24, 2023

Last Modified

February 26, 2026

Advisory Details (2)

Auto-updated Jul 27, 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-2023-33009
generic

Zyxel security advisory for multiple buffer overflow vulnerabilities of firewalls | Zyxel Networks

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-buffer-overflow-vulnerabilities-of-firewalls

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 41× 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 481 total refreshes for this CVE.

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

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Frequently asked(6)

What is CVE-2023-33009?
CVE-2023-33009 is a critical vulnerability published on May 24, 2023. A buffer overflow vulnerability in the notification function in Zyxel ATP series firmware versions 4.60 through 5.36 Patch 1, USG FLEX series firmware versions 4.60 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.60 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.60 through 5.36…
When was CVE-2023-33009 disclosed?
CVE-2023-33009 was first published in the National Vulnerability Database on May 24, 2023, with the most recent update on February 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-33009 actively exploited?
Yes. CISA added CVE-2023-33009 to the Known Exploited Vulnerabilities catalog on June 5, 2023, affecting Zyxel Multiple Firewalls. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2023-33009?
CVE-2023-33009 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2023-33009?
CVE-2023-33009 affects Zyxel Multiple Firewalls. 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-2023-33009?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-33009, 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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