CVE-2026-84317

## Summary `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). ## Root cause — an incomplete hardening patch Commit `3e411d38` ("Harden config write paths", 2026-04-21) introduced `ValidateConfigFile` and wired it into the config-write paths — but its changeset touched only: api/config/add.go (+6), api/config/modify.go (+8), internal/config/validation.go (+199), mcp/config/config_modify.go (+5) It did NOT touch `mcp/config/config_add.go`. So the MCP add path was left without the validation that all of its sibling paths received. `config_add.go` has never called `ValidateConfigFile` (verified via git history); this is an oversight in the hardening, not a regression. ## Affected code (mcp/config/config_add.go, handleNginxConfigAdd) ```go content := mcp.GetString(args, "content") // caller-controlled ... path, err := config.ResolveConfPath(baseDir, name) // path is sandboxed to the conf dir (OK) ... err = os.WriteFile(path, []byte(content), 0644) // <-- no config.ValidateConfigFile(path, content) ... res := nginx.Control(nginx.Reload) // reloads nginx ``` Contrast — the guarded sibling (mcp/config/config_modify.go) does: ```go err = config.ValidateConfigFile(absPath, content) // rejects js_*/perl_*/load_module/user root if err !=