HighVulnerability

CVE-2026-84317: Nginx UI MCP config add tool skips validation, allowing dangerous directives

Source: NVD(opens in a new tab)
Identifier: CVE-2026-84317
Published: October 12, 2026
Record updated: October 12, 2026

Known exploitation: Not listed in the CISA Known Exploited Vulnerabilities catalog at the last check.

Summary

Nginx UI, a web user interface for the Nginx web server, has a flaw in versions prior to 2.4.1. Its validation control, ValidateConfigFile in internal/config/validation.go, blocks dangerous directives such as js_*, perl_*, load_module for the njs and perl modules, and user root, but the MCP tool nginx_config_add (mcp/config/config_add.go) never calls it and writes caller-supplied content directly to disk before reloading nginx. An authenticated MCP caller, or an MCP agent manipulated through prompt injection, can therefore inject the blocked directives and achieve code execution in nginx on deployments where the njs or perl module is available, such as the official Docker image.

Mitigation

Fixed in version 2.4.1.

Details

Scores and exploitation

CVSS score: 8.8(high)
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector: network
Attack complexity: low
Privileges required: low
User interaction: none
EPSS: Not scored. FIRST had not published an EPSS score for this CVE when it was last checked on October 12, 2026.
Disclosure date: October 12, 2026

Weaknesses and techniques

Weakness (CWE): CWE-20
CWE-693

Classification

Attack type: Other
Attack sophistication: Moderate
AI component targeted: Plugin
Impact: Confidentiality,
Integrity,
Availability,
Safety
Labels: security

How this record was produced

Summaries, mitigations and labels on this page are generated automatically from the source. The linked source is authoritative. The source gives this advisory a description and no title, so the title above is a headline generated from the source text.

Original source: https://nvd.nist.gov/vuln/detail/CVE-2026-84317

First tracked: October 12, 2026 at 08:08 PM ET, from NVD/CVE Database

Classifier: claude-haiku-5-5, prompt v4

Classifier confidence: 80% (self-assessed)

Topics

Model Context Protocol

Summary

Mitigation

Topics

Related items