CVE-2026-42221
nginx-ui: Unauthenticated First-Run Installer Allows Remote Initial Admin Claim
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.
INFO
Published Date :
May 4, 2026, 9:16 p.m.
Last Modified :
May 6, 2026, 5:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Update Nginx UI to version 2.3.8.
- Apply security patches promptly.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-42221.
| URL | Resource |
|---|---|
| https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8 | Release Notes |
| https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp | Exploit Mitigation Vendor Advisory |
| https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp | Exploit Mitigation Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-42221 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-42221
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-42221 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-42221 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
May. 06, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:nginxui:nginx_ui:*:*:*:*:*:*:*:* versions from (including) 2.0.0 up to (excluding) 2.3.8 Added Reference Type GitHub, Inc.: https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8 Types: Release Notes Added Reference Type CISA-ADP: https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp Types: Exploit, Mitigation, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp Types: Exploit, Mitigation, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 05, 2026
Action Type Old Value New Value Added Reference https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp -
New CVE Received by [email protected]
May. 04, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-306 Added Reference https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8 Added Reference https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp