nginx-ui: Protection mechanism bypass in MCP configuration interface
Summary
Nginx UI, a web interface for managing Nginx, does not apply its restricted-directive check to the MCP configuration interface. An authenticated secondary user can therefore write restricted directives such as load_module and js_import, load the NJS module, and execute attacker-controlled JavaScript in the Nginx worker context. The attack requires a valid user account, MCP to be enabled and the NJS module to be available.
Affected
- nginx-ui versions before 2.4.1
Fixed in
- Fixed in version 2.4.1 (fix commits 23d1934099b05b2a01589b48129dc3d3159d91c2 and 0540f3ecf7824e9adbe408f3166d151651ccf4dd per OSV)
- Later releases (for example 2.4.2) exist; it is unknown whether they contain additional fixes for this issue
Workaround
- No official workaround published.
- Disable the MCP interface if it is not required.
- Restrict access to the nginx-ui administration interface to trusted networks.
- Review which accounts have access to nginx-ui.
Exploitation
- Not known to be exploited in the wild; not listed in the CISA KEV catalog according to a third-party source.
- No public proof of concept identified (unverified).
- EPSS about 0.0028 (Vulners).
- CISA SSVC: Exploitation none, Automatable no, Technical Impact partial.
Our recommendation
- Update nginx-ui to the latest stable release, at least 2.4.1.
- Check whether the MCP interface is enabled and disable it if not needed.
- Review user accounts and remove unneeded secondary accounts; enforce strong passwords.
- Limit nginx-ui access to trusted administrators and networks.
- Monitor Nginx configuration changes for unexpected load_module or js_import directives.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-5r62-gj48-897x github.com
- Fix commit 23d1934 github.com
- Release v2.4.1 github.com
- OSV CVE-2026-84319 osv.dev
- OpenCVE CVE-2026-84319 app.opencve.io
- Vulners RAPID7:CVE-2026-84319 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 13:55.
Original description (NVD)
Nginx UI is a web user interface for the Nginx web server. Prior to 2.4.1, the regular HTTP configuration API rejects restricted Nginx directives such as load_module, js_import, and js_content. However, the MCP configuration interface allows a secondary authenticated user to write and apply equivalent restricted configuration content. This allows the user to load ngx_http_js_module.so, import attacker-controlled JavaScript, reload Nginx, and execute NJS in the Nginx worker context. This issue is fixed in version 2.4.1.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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