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CVE-2026-42221

nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim

Published: May 4, 2026Updated: May 6, 2026 Sources: CVE List NVD BDUCWE-306
NVD MITRE
8.1CVSSHIGH
EPSS Score
0.3%
Top 73.8%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

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 Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-306

Affected Products

nginx-ui0xJacky
Mixed
Cloud & SaaS / saas-application
Nginx UIСообщество свободного программного обеспечения
On-prem
Web & CMS Plugins
nginx uinginxui
On-prem
Networking Infrastructure / network-management
0xjackyindividual-devCloud & SaaSaka nginx-ui
сообщество свободного программного обеспеченияoss-projectOperating Systemsaka сообщество свободного программного обеспечения, fsf
nginxuicommercialNetworking Infrastructureaka nginx ui, nginxui

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available
Workaround Available

MITRE ATT&CK

2 techniques
Initial Access
View detailed technique mapping

References

https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp
github.com
https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8
github.com
https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8
github.com

Timeline

Published
May 4, 2026
Last Updated
May 6, 2026

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