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: 0.003 (26.9th 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)
Public proof-of-concept exploits
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
- security-advisories@github.com (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.
- Is CVE-2026-42221 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.