{"id":"CVE-2026-42221","aliases":["GHSA-h27v-ph7w-m9fp","GO-2026-5412"],"url":"https://o3.security/vulnerability/CVE-2026-42221","summary":"nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim","details":"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.","published":"2026-05-04T20:09:37.308Z","modified":"2026-08-05T03:32:34.771668812Z","cvss":{"score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/0xJacky/Nginx-UI","fixedVersion":"2.3.8"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8"},{"type":"ADVISORY","url":"https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42221.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42221"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-05T03:32:34.771668812Z"}}