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Vulnerabilities

Vulnerability · CVE-2026-84319

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

Published Oct 12, 2026 · catalog updated Oct 15, 2026 · 0xJacky

Check if you run it

No confirmed exploitation is on record for CVE-2026-84319. EPSS is 0.28%. Act only if a listed version of 0xJacky is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.28%
Remediation
Advisory link
Affected products
Go github.com/0xJacky/Nginx-UI · golang github.com · vendor 0xJacky nginx-ui

## Summary The regular HTTP configuration API rejects restricted Nginx directives such as , , and . 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 , 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 tool: - 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 enabled. - Nginx has NJS available: Observed in the lab: ### 1. HTTP API blocks the restricted config Request: Body: Observed result: ### 2. MCP writes the JavaScript file Open an MCP session and call with: ### 3. MCP writes the NJS-enabled nginx.conf Call again: ### 4. Verify NJS execution Inside the Nginx UI container: Observed response: This confirms that content rejected by the HTTP API can be applied through MCP and executed as NJS in the Nginx worker context. ## Expected behavior MCP configuration tools should enforce the same restricted directive validation as the HTTP API. ## Suggested fix Apply before MCP configuration writes and ensure HTTP API and MCP share the same validation tests for restricted directives such as: - - - - - -

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Go github.com/0xJacky/Nginx-UI0 → 1.9.10-0.20260703131214-23d1934099b0
  • golang github.comversion unspecified
  • vendor 0xJacky nginx-uiversion unspecified

How to fix CVE-2026-84319

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-84319. EPSS is 0.28%. Act only if a listed version of 0xJacky is installed.

Which versions are affected?

Compare what you have installed with github.com/0xJacky/Nginx-UI 0 → 1.9.10-0.20260703131214-23d1934099b0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-693: Protection Mechanism Failure. EPSS 0.28%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Nginx security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 15, 2026 · GitHub Advisory Database

    Detected

    ## Summary The regular HTTP configuration API rejects restricted Nginx directives such as , , and . 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 , import attacker-controlled JavaScript, reload Nginx, and execute NJS in the Nginx worker context. This is authent

  2. Oct 15, 2026 · GitHub Advisory Database

    Fix available

    github.com/0xJacky/Nginx-UI fixed in 1.9.10-0.20260703131214-23d1934099b0

  3. Oct 15, 2026 · GitHub Advisory Database

    Fix available

    github.com/0xJacky/Nginx-UI fixed in 1.9.10-0.20260703131214-23d1934099b0

  4. Oct 15, 2026 · GitHub Advisory Database

    Updated

    ## Summary The regular HTTP configuration API rejects restricted Nginx directives such as , , and . 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 , import attacker-controlled JavaScript, reload Nginx, and execute NJS in the Nginx worker context. This is authent

Sources

  • CVE.orgVulnerability recordCVE-2026-84319

    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 writ

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-84319

    30-day exploitation probability 0.3%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-5r62-gj48-897x

    GitHub Advisory Database record mirrored by OSV.

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-84319

    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. In the lab, this allowed the user to load ngx_http_js_module.so, import attacker-controlled JavaScript, reload Nginx, and execute NJS in t

    advisories.gitlab.com
  • OpenSSF OSV / OSV ScannerPackage advisoryGHSA-5r62-gj48-897x

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

    osv.dev

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.