CVE-2026-84317: CWE-20: Improper Input Validation in 0xJacky nginx-ui
Description
CVE-2026-84317 is a high-severity vulnerability in 0xJacky's nginx-ui prior to version 2.4.1. It involves improper input validation in the MCP tool's config add functionality, which bypasses security controls designed to block dangerous nginx directives. This allows an authenticated MCP caller to inject malicious directives, potentially leading to nginx code execution on deployments with the njs or perl modules available. The issue is fixed in version 2.4.1.
CVSS v3.1
Score 8.8high
Affected software
0xJacky
nginx-ui
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Nginx UI is a web interface for managing the Nginx web server. Its security control ValidateConfigFile blocks dangerous directives such as js_*, perl_*, load_module of njs/perl modules, and user root on three config-write paths. However, the MCP tool's nginx_config_add path does not invoke this validation and writes user-supplied content directly to disk and reloads nginx. This flaw allows an authenticated MCP caller or an MCP agent induced via prompt injection to inject blocked directives, enabling code execution if njs or perl modules are present. The vulnerability is resolved in version 2.4.1.
Potential Impact
An authenticated attacker with access to the MCP tool can bypass input validation and inject dangerous nginx directives, leading to remote code execution on affected deployments that have the njs or perl modules enabled. This compromises confidentiality, integrity, and availability of the nginx server.
Mitigation Recommendations
This vulnerability is fixed in nginx-ui version 2.4.1. Users should upgrade to version 2.4.1 or later to remediate this issue. No other mitigations are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-09-01T16:17:43.079Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6acd4ec92cdf04f656d63e57
Added to database: 10/12/2026, 21:19:05 UTC
Last enriched: 10/12/2026, 21:33:20 UTC
Last updated: 10/12/2026, 21:33:55 UTC
Views: 4
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