CVE-2026-42221

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 72% 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
Elevated
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 8.1Exploit: Elevated riskExposed: 0

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

Nginx UI is a web user interface for the Nginx web server. From version 2.0.0 to before version 2.3.8, an unauthenticated network attacker can claim the initial administrator account on a fresh nginx-ui instance during the first-run setup window. The public /api/install endpoint is reachable without authentication, and the request-encryption flow only protects payload confidentiality in transit; it does not authenticate who is allowed to perform installation. A remote attacker who reaches the service before the legitimate operator can set the admin email, username, and password, causing permanent initial-instance takeover. This issue has been patched in version 2.3.8.

CVSS v3
8.1
EG Score
8.1(medium)
EG Risk
52(Track*)
EG Risk 52/100SSVC: 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
Severity81% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
1%
EPSS %ILE
66%
KEV
Not listed

Published

May 4, 2026

Last Modified

May 6, 2026

Advisory Details (2)

Auto-updated May 4, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Unauthenticated First-Run Installer Allows Remote Initial Admin Claim · Advisory · 0xJacky/nginx-ui · GitHub

https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp
generic

Release v2.3.8 · 0xJacky/nginx-ui · GitHub

https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8

Affected Packages

(1 across 1 ecosystem)
Go(1)
PackageVulnerable rangeFixed inDependents
github.com/0xJacky/Nginx-UI—2.3.8—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 27× 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 145 total refreshes for this CVE.

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

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2026/CVE-2026-42221.yaml
    First seen Jan 1, 2026

    Nginx UI <= 2.3.7 - Unauthenticated Installer Exposure

    Open source ↗

Frequently asked(5)

What is CVE-2026-42221?
CVE-2026-42221 is a high vulnerability published on May 4, 2026. Nginx UI is a web user interface for the Nginx web server. From version 2.0.0 to before version 2.3.8, an unauthenticated network attacker can claim the initial administrator account on a fresh nginx-ui instance during the first-run setup window. The public /api/install endpoint is reachable…
When was CVE-2026-42221 disclosed?
CVE-2026-42221 was first published in the National Vulnerability Database on May 4, 2026, with the most recent update on May 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42221 actively exploited?
CVE-2026-42221 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 34.5% of all scored CVEs.
What is the CVSS score of CVE-2026-42221?
CVE-2026-42221 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2026-42221?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42221, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-42221

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