Vulnerability details
CVE-2026-42221
nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
Official description
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 scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 8.1High | 3.1 | CVEProject cvelistV5 (CNA) (GitHub_M) | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| 0xJacky | nginx-ui | >= 2.0.0, < 2.3.8 | CVEProject cvelistV5 (CNA) |
References and advisories
2- https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8 x_refsource_MISC
- https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp x_refsource_CONFIRM
Details
- Published
- 2026-05-04
- Last updated
- 2026-05-05
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
SSVC assessment (CISA)
- Automatable
- No
- Exploitation
- Proof of concept
- Technical impact
- Total
Weaknesses (CWE)
- CWE-306Missing Authentication for Critical Function