[ CVE-2026-84318 · Published 12 Oct 2026 ]
Nginx UI: MCP `nginx_config_add` Bypasses Directive Validation — Authenticated RCE
CVSS 8.8
EPSS <1%Fix available
[ Why it matters ]Priority signals
- Public proof-of-concept exploit exists (CISA SSVC)
[ Description ]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.
[ Fixes ]Fixes and patches
- github.com/0xJacky/Nginx-UI 1.9.10-0.20260703131214-23d1934099b0Fixed version · GitHub Advisories · go package github.com/0xJacky/Nginx-UI: upgrade to 1.9.10-0.20260703131214-23d1934099b0 or later (affected >= 1.9.10-0.20250506154222-1330888280a2, < 1.9.10-0.20260703131214-23d1934099b0)
[ Packages ]Affected open-source packages
- github.com/0xJacky/Nginx-UI goAffected >= 1.9.10-0.20250506154222-1330888280a2, < 1.9.10-0.20260703131214-23d1934099b0 · fixed in 1.9.10-0.20260703131214-23d1934099b0 · GHSA-9jww-cxg5-rj9m