0xJacky nginx-ui up to 2.4.0 MCP Tool mcp/config/config_add.go nginx_config_add input validation

Summaryinfo

A vulnerability classified as very critical was found in 0xJacky nginx-ui up to 2.4.0. Affected by this issue is the function nginx_config_add of the file mcp/config/config_add.go of the component MCP Tool. Such manipulation leads to input validation. This vulnerability is uniquely identified as CVE-2026-84317. The attack can be launched remotely. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in 0xJacky nginx-ui up to 2.4.0. Affected by this issue is the function nginx_config_add of the file mcp/config/config_add.go of the component MCP Tool. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Nginx UI is a web user interface for the Nginx web server. Prior to 2.4.1, internal/config/validation.go (ValidateConfigFile) is a security control that blocks dangerous nginx directives — js_*, perl_*, load_module of the njs/perl modules, and user root. It is enforced on three of the four config-write paths: api/config/add.go, api/config/modify.go, and mcp/config/config_modify.go. The fourth path — the MCP tool nginx_config_add (mcp/config/config_add.go) — does NOT call it: it writes the caller-supplied content straight to disk and reloads nginx. An authenticated MCP caller (or an MCP agent induced via prompt injection) can therefore inject exactly the directives the control is meant to block, leading to nginx code execution on deployments where the njs/perl module is available (e.g. the official Docker image). This issue is fixed in version 2.4.1.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-84317 since 09/01/2026. The exploitation is known to be easy. The attack may be launched remotely. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/12/2026).

Upgrading to version 2.4.1 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Web Server

Vendor

• 0xJacky

Name

• nginx-ui

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4.0

Website

• Product: https://github.com/0xJacky/nginx-ui/

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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