CVE-2026-42221
nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
No known exploitation. EPSS puts it in the 76th percentile. Fixed in 2.3.8.
What to do
Find your product and version, then upgrade to the build on the right.
- 0xJacky nginx-uiAffected: >= 2.0.0, < 2.3.8Upgrade to: not statedStated by: CVE record
- Nginxui Nginx UiAffected: ≥ 2.0.0, < 2.3.8Upgrade to: 2.3.8Stated by: NVD
- Сообщество свободного программного обеспечения Nginx UIAffected: от 2.0.0 до 2.3.8Upgrade to: not statedStated by: BDU
Versions as the sources state them. Full version matrix after sign-in
What it is
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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
1.6% chance of exploitation activity in the next 30 days, which ranks it in the 76th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
8 events over 126 days, from the signal feeds we watch.
- Nuclei check added
- OpenVAS check added
- Patch availableworkaround available, record updated
- Publishedweakness classified, att&ck mapped
Affected products
Technical detail
CVSS 3.1 vector
Open in the CVSS calculatorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Scored 8.1 by NVD.
How it is reached
- Attack Vector NetworkExploitable remotely over the network without any special conditions
- Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
- Privileges Required NoneNo authentication required — anyone can exploit this
- User Interaction NoneNo user interaction needed — fully automated exploitation
Scope
- Scope UnchangedImpact is limited to the vulnerable component itself
Impact if exploited
- Confidentiality HighTotal information disclosure — all data in the component is compromised
- Integrity HighTotal loss of integrity — attacker can modify any data in the component
- Availability HighTotal denial of service — the component is completely unavailable
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
Sources
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