# CVE-2026-42222: Nginx-UI: Unauthenticated first-boot instance claim via POST /api/install allows remote bootstrap takeover

Source: https://junglewise.ai/threats/cve-2026-42222-nginx-ui-unauthenticated-first-boot-instance-claim-via-post-api  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-04  
License: CC BY 4.0 with a link back

CVE-2026-42222 · Severity: high · CVSS 8.1 · Published 2026-05-04

Nginx UI is a web user interface for the Nginx web server. In version 2.3.5, an unauthenticated bootstrap takeover exists in nginx-ui during the initial installation window exposed by POST /api/install. At time of publication no public patches are available.

Technologies: [github.com/0xJacky/Nginx-UI (Go)](https://junglewise.ai/threats/technologies/github-com-0xjacky-nginx-ui), [Nginxui Nginx Ui](https://junglewise.ai/threats/technologies/nginxui-nginx-ui). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Nginxui](https://junglewise.ai/threats/vendors/nginxui).

## Quick answers

**Is CVE-2026-42222 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42222 being exploited in the wild.

**How severe is CVE-2026-42222?** High severity, with a CVSS score of 8.1, published 4 May 2026.

**Which products and versions are affected?** github.com/0xJacky/Nginx-UI (Go) SEMVER:introduced=0.

**Is there a fix for CVE-2026-42222?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2026-42222?** Check whether you run github.com/0xJacky/Nginx-UI (Go) or Nginxui Nginx Ui at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- github.com/0xJacky/Nginx-UI (Go) SEMVER:introduced=0
- Nginxui Nginx Ui

## Identifiers

- CVE-2026-42222
- GHSA-mxqh-q9h6-v8pq
- GO-2026-5521

## Related threats

- [Nginx UI Casdoor SSO login CSRF via constant state parameter](https://junglewise.ai/threats/cve-2026-84312-nginx-ui-casdoor-sso-callback-uses-a-constant-state-parameter)
- [Nginx UI OTP secure-session step-up bypass via MCP](https://junglewise.ai/threats/cve-2026-84360-nginx-ui-otp-secure-session-step-up-can-be-bypassed-via-mcp)
- [Nginx UI short token cache bypass after account re-enable](https://junglewise.ai/threats/cve-2026-84321-nginx-ui-standalone-short-tokens-survive-administrative)
- [Nginx UI auto backup path traversal in storage boundary](https://junglewise.ai/threats/cve-2026-84320-nginx-ui-auto-backup-name-allows-path-traversal-outside-validated)
- [Nginx UI MCP configuration directive validation bypass](https://junglewise.ai/threats/cve-2026-84319-nginx-ui-mcp-configuration-tools-bypass-restricted-directive)