{"id":"CVE-2026-42221","sourceIdentifier":"security-advisories@github.com","published":"2026-05-04T21:16:32.023","lastModified":"2026-06-17T10:47:31.917","vulnStatus":"Analyzed","cveTags":[],"descriptions":[{"lang":"en","value":"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":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"0xJacky","product":"nginx-ui","versions":[{"version":">= 2.0.0, < 2.3.8","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.2,"impactScore":5.9},{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-05-05T14:06:26.362325Z","id":"CVE-2026-42221","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-306"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:nginxui:nginx_ui:*:*:*:*:*:*:*:*","versionStartIncluding":"2.0.0","versionEndExcluding":"2.3.8","matchCriteriaId":"623A6AFE-E1C3-4D21-9465-A33CB945AF6F"}]}]}],"references":[{"url":"https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8","source":"security-advisories@github.com","tags":["Release Notes"]},{"url":"https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp","source":"security-advisories@github.com","tags":["Exploit","Mitigation","Vendor Advisory"]},{"url":"https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":["Exploit","Mitigation","Vendor Advisory"]}]}