CVE-2026-42221: high-severity vulnerability in 0xJacky nginx-ui
nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
Published · Updated
56Vexday Risk Score
Patch soon. It has a working public exploit.
ssvc Attendcvss 8.1epss 1.6%
from disclosure to weapon50 days
Published on NVDMay 4
1st PoC+50d
exploitation probability
1.6%top 25% of all CVEs
observed exploitation
nono source reports it
1 public exploit(s)
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:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Affected products
0xJacky · nginx-uipublic PoCs found — 1
githubgithub.com/fuchiuebusi-lab/nginx-ui-CVE-2026-42221-CVE-2026-42238-★ 0⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
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