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

> Unauthenticated attackers can claim the initial installation instance via the install API, gaining administrative control over the Nginx UI.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 May 2026
- **Updated:** 6 May 2026
- **Also known as:** GHSA-mxqh-q9h6-v8pq, GO-2026-5521

## What is CVE-2026-42222?

CVE-2026-42222 is a high-severity authentication bypass vulnerability in 0xJacky nginx-ui, published on 4 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-306 (Missing Authentication for Critical Functionality), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-42222?

3 open source packages ship an affected version, including github.com/0xJacky/nginx-ui. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/0xJacky/nginx-ui` | Go | All versions | None |
| `github.com/0xJacky/nginx-ui` | Go | All versions | None |
| `github.com/0xJacky/nginx-ui` | Go | All versions | None |

Products: Nginxui Nginx Ui.

## How do I fix CVE-2026-42222?

No fix published yet.

## Is CVE-2026-42222 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42222 exists.

## Other vulnerabilities in 0xJacky nginx-ui

- [CVE-2026-33032](https://insights.sbomify.com/CVE-2026-33032/): Nginx UI: Unauthenticated MCP Endpoint Allows Remote Nginx Takeover (critical 9.8)
- [CVE-2026-27944](https://insights.sbomify.com/CVE-2026-27944/): Nginx UI: Unauthenticated Backup Download with Encryption Key Disclosure (critical 9.8)
- [CVE-2024-23827](https://insights.sbomify.com/CVE-2024-23827/): Nginx-UI arbitrary file write through the Import Certificate feature (critical 9.8)
- [CVE-2026-107806](https://insights.sbomify.com/CVE-2026-107806/): Nginx UI: Authenticated Remote Code Execution via Backup Restore App Config Overwrite (critical 9.4)
- [CVE-2026-33026](https://insights.sbomify.com/CVE-2026-33026/): nginx-ui Backup Restore Allows Tampering with Encrypted Backups (critical 9.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42222 and fix it if it is affected.

What it is: CVE-2026-42222 is a high-severity authentication bypass vulnerability in 0xJacky nginx-ui, published on 4 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42222 exists.

Affected packages and fixed versions:
- github.com/0xJacky/nginx-ui (Go): affected all versions; no fix listed
- github.com/0xJacky/nginx-ui (Go): affected all versions; no fix listed
- github.com/0xJacky/nginx-ui (Go): affected all versions; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42222/ (Markdown: https://insights.sbomify.com/CVE-2026-42222/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42222
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42222
- OSV: https://osv.dev/vulnerability/CVE-2026-42222

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42222/
Summaries are generated and may contain mistakes; the official description above is the record.