CVE-2026-84318
Nginx UI: MCP `nginx_config_add` Bypasses Directive Validation — Authenticated RCE
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/0xJacky/Nginx-UI | >= 1.9.10-0.20250506154222-1330888280a2, < 1.9.10-0.20260703131214-23d1934099b0 | 1.9.10-0.20260703131214-23d1934099b0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-9jww-cxg5-rj9m
- https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-9jww-cxg5-rj9m
- https://nvd.nist.gov/vuln/detail/CVE-2026-84318
- https://github.com/0xJacky/nginx-ui/commit/23d1934099b05b2a01589b48129dc3d3159d91c2
- https://github.com/0xJacky/nginx-ui/releases/tag/v2.4.1