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CVE-2026-42221

37
FAUCET Score

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.

First published: May 4, 2026Last modified: May 5, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 2.0.0, < 2.3.8CPE matchmatch criteria
cpe:2.3:a:nginxui:nginx_ui:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.1HIGH

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.35%
Probability of exploitation in next 30 days
EPSS Percentile
27.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0035 is in the 5th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

gopatch availablevia ghsa
Product: github.com/0xJacky/Nginx-UIFixed in: 2.3.8
github_advisoryworkaround availablevia nvd_reference
View patch

Vendor Advisories (1)

goGHSA-h27v-ph7w-m9fphigh

Nginx-UI: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim

May 6, 2026

References

github.com / 0xJacky/nginx-ui/releases/tag/v2.3.8
Release Notes
github.com / 0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp
ExploitMitigationVendor Advisory