CVE-2026-84316: Nginx UI: nginx config directive denylist (ValidateConfigFile) is bypassable via same-line ";" separation → authenticated directive injection (RCE on the official image)

Vulnerability summary

CVE-2026-84316 is a high (CVSS 8.8) Improper Input Validation vulnerability in 0xjacky nginx-ui. EPSS estimates a 0.51% chance of exploitation in the next 30 days, higher than 43.3% of scored vulnerabilities.

Timeline

1. 12-10-2026
   PublishedVulnerability first disclosed.
2. 13-10-2026
   Last modifiedVulnerability information updated.

Description

Nginx UI is a web user interface for the Nginx web server. Prior to 2.4.1, config.ValidateConfigDirectives splits configuration by newline and checks only the first directive token on each line even though Nginx permits multiple semicolon-separated directives on one line. An authenticated caller can place a benign directive first and a restricted load_module, js_import, perl, or user root directive later on the same line, or can use an unrestricted include directive to load restricted content. These mechanisms bypass validation on REST, nginx_config_modify, site, and stream write paths; when an executable module is available, the injected configuration can execute code in the Nginx worker context. This issue is fixed in version 2.4.1.

• CWE-20Improper Input ValidationThe 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.
• CWE-184Incomplete List of Disallowed InputsThe product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete.