# CVE-2026-84318: Nginx UI: MCP `nginx_config_add` Bypasses Directive Validation — Authenticated RCE

> An authenticated attacker can bypass directive validation in the MCP tool to write malicious Nginx configs, leading to remote code execution.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Oct 2026
- **Updated:** 13 Oct 2026
- **Also known as:** GHSA-9jww-cxg5-rj9m, GO-2026-6781

## What is CVE-2026-84318?

CVE-2026-84318 is a high-severity missing authorization vulnerability in 0xJacky nginx-ui, published on 12 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Nginx UI is a web user interface for the Nginx web server. From 2.0.0-rc.6 until 2.4.1, the MCP tool nginx_config_add writes nginx configuration files to disk and triggers an nginx reload without calling config.ValidateConfigFile. The identical flow in the REST API (POST /api/configs) does call that function and correctly rejects dangerous directives. An authenticated attacker can exploit this gap to write config files containing any blocked directive (perl, js_import, load_module, user root, etc.), bypassing nginx-ui's entire security layer. On a server with the nginx Perl, njs, or Lua module loaded, this is post-authentication Remote Code Execution. This issue is fixed in version 2.4.1.

Weakness: CWE-693 (Protection Mechanism Failure)

## Which versions are affected by CVE-2026-84318?

3 open source packages ship an affected version, including github.com/0xJacky/Nginx-UI.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/0xJacky/Nginx-UI` | Go | From 1.9.10-0.20250506154222-1330888280a2 | 1.9.10-0.20260703131214-23d1934099b0 |
| `github.com/0xJacky/Nginx-UI` | Go | From 1.9.10-0.20250506154222-1330888280a2 | 1.9.10-0.20260703131214-23d1934099b0 |
| `github.com/0xJacky/Nginx-UI` | Go | From 1.9.10-0.20250506154222-1330888280a2 | 1.9.10-0.20260703131214-23d1934099b0 |

## How do I fix CVE-2026-84318?

Upgrade github.com/0xJacky/Nginx-UI to 1.9.10-0.20260703131214-23d1934099b0 or later.

## Is CVE-2026-84318 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84318 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84318 and fix it if it is affected.

What it is: CVE-2026-84318 is a high-severity missing authorization vulnerability in 0xJacky nginx-ui, published on 12 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84318 exists.

Affected packages and fixed versions:
- github.com/0xJacky/Nginx-UI (Go): affected from 1.9.10-0.20250506154222-1330888280a2; fixed in 1.9.10-0.20260703131214-23d1934099b0
- github.com/0xJacky/Nginx-UI (Go): affected from 1.9.10-0.20250506154222-1330888280a2; fixed in 1.9.10-0.20260703131214-23d1934099b0
- github.com/0xJacky/Nginx-UI (Go): affected from 1.9.10-0.20250506154222-1330888280a2; fixed in 1.9.10-0.20260703131214-23d1934099b0

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-2026-84318/ (Markdown: https://insights.sbomify.com/CVE-2026-84318/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84318
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84318
- OSV: https://osv.dev/vulnerability/CVE-2026-84318

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84318/
Summaries are generated and may contain mistakes; the official description above is the record.