What is CVE-2026-42221?

CVE-2026-42221 is a high-severity vulnerability in 0xjacky Nginx-ui, classified under Missing Authentication for Critical Function. CVSS score: 8.1/10. Published 2026-05-04.

How severe is CVE-2026-42221?

High severity. CVSS v3 base score is 8.1 out of 10.

Auth bypass in 0xjacky Nginx-ui

CVE-2026-42221

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…

Vulnerability class: Broken Authentication

EPSS: 0.001 (26.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

0xjacky Nginx-ui — versions >= 2.0.0, < 2.3.8
Nginxui Nginx_ui

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

References

https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8 (x_refsource_MISC, Release Notes)

Frequently asked questions

What is CVE-2026-42221?: CVE-2026-42221 is a high-severity vulnerability in 0xjacky Nginx-ui, classified under Missing Authentication for Critical Function. CVSS score: 8.1/10. Published 2026-05-04.
How severe is CVE-2026-42221?: High severity. CVSS v3 base score is 8.1 out of 10.