vulnerability / NVI-00011986 / Revision 2
Nginx UI: MCP `nginx_config_add` Bypasses Directive Validation — Authenticated RCE
GitHub lists this reviewed advisory for github.com/0xJacky/Nginx-UI. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
8.8 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
0.816%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.57203. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
github.com/0xJacky/Nginx-UI
source listed>= 1.9.10-0.20250506154222-1330888280a2, < 1.9.10-0.20260703131214-23d1934099b0
### Summary The MCP tool `nginx_config_add` writes nginx configuration files to disk and triggers an nginx reload without calling `config.ValidateConfigFile`. The identical flow in the REST API (`POST /api/configs`) does call that function and correctly rejects dangerous directives. An authenticated attacker can exploit this gap to write config files containing any blocked directive (`perl`, `js_import`, `load_module`, `user root`, etc.), bypassing nginx-ui's entire security layer. On a server with the nginx Perl, njs, or Lua module loaded, this is post-authentication Remote Code Execution. ### Details `api/config/add.go` (line 46) calls `config.ValidateConfigFile` before writing: ```go err = config.ValidateConfigFile(path, content) // validates directives, checks blocklist if err != nil { cosy.ErrHandler(c, err) return } ``` `mcp/config/config_add.go` (line 79) omits that call entirely and writes directly: ```go err = os.WriteFile(path, []byte(content), 0644) // no ValidateConfigFile, no blocklist check ... res := nginx.Control(nginx.Reload) // reload triggered immediately ``` `config.ValidateConfigFile` runs two checks: - **`ValidateConfigContent`**
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-9jww-cxg5-rj9m ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-84318 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.