Nginx UI: MCP configuration tools bypass restricted directive validation and allow secondary authenticated users to execute NJS in Nginx worker context

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H

EPSS

• CVE-2026-84319: 0.28% estimated exploitation activity in the next 30 days; percentile 20.59 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The regular HTTP configuration API rejects restricted Nginx directives such as loadmodule, jsimport, and jscontent. However, the MCP configuration interface allows a secondary authenticated user to write and apply equivalent restricted configuration content. In the lab, this allowed the user to load ngxhttpjsmodule.so, import attacker-controlled JavaScript, reload Nginx, and execute NJS in the Nginx worker context. This is authenticated and is not OS command execution by itself. Affected component - /mcp - /mcpmessage - MCP tool: nginxconfigadd - Nginx configuration validation Impact A secondary authenticated user can bypass the restricted directive validation enforced by the HTTP API and execute attacker-controlled NJS inside the Nginx worker context. This may allow modification of Nginx runtime behavior, including responses, routing, headers, redirects, and request handling. Minimal PoC Preconditions - Attacker has a secondary authenticated Nginx UI account. - MCP is…

Published by the source

15 Oct 2026, 20:10 UTC

Last modified by the source

19 Oct 2026, 21:31 UTC

Source last checked

26 Oct 2026, 15:32 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5r62-gj48-897x

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6774

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-5r62-gj48-897x

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# Patch Next advisory brief: CVE-2026-84319

Advisory: Nginx UI: MCP configuration tools bypass restricted directive validation and allow secondary authenticated users to execute NJS in Nginx worker context
IDs: CVE-2026-84319, GHSA-5r62-gj48-897x
Record: https://patchnext.com/advisories/cve-2026-84319 (revision 3, source checked 26 Oct 2026, 15:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/0xJacky/Nginx-UI 1.9.10-0.20260703131214-23d1934099b0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/0xJacky/Nginx-UI: affected < 1.9.10-0.20260703131214-23d1934099b0; fixed in 1.9.10-0.20260703131214-23d1934099b0

## Suggested inspection (read-only)
- Go github.com/0xJacky/Nginx-UI: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/0xJacky/Nginx-UI.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5r62-gj48-897x (OSV record GHSA-5r62-gj48-897x lists affected ranges: Go github.com/0xJacky/Nginx-UI >=0 <1.9.10-0.20260703131214-23d1934099b0 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6774 (OSV record GO-2026-6774 lists affected ranges: Go github.com/0xJacky/Nginx-UI >=0 <1.9.10-0.20260703131214-23d1934099b0 (fixed))
- Verified: https://github.com/advisories/GHSA-5r62-gj48-897x (GitHub-reviewed advisory GHSA-5r62-gj48-897x lists affected ranges: Go github.com/0xJacky/Nginx-UI >=0 <1.9.10-0.20260703131214-23d1934099b0)

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