by Kastro
Paper/Archive/CVE-2026-42221

CVE-2026-42221

0xJacky nginx-ui — nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim

EPSS 1%public exploitCVSS 9.8
critical.is priorityof 100
54
CVSS 9.8 (NVD)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 71.3.713 × 2014.3Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
nginx-ui>= 2.0.0, < 2.3.8–CNA

Scores by source

NVD9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub_M (CNA)8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA ADPSSVCExploitation: poc · Automatable: no · Technical impact: total

References

exploitgithub.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fprefgithub.com/0xJacky/nginx-ui/releases/tag/v2.3.8