owasp-amass/amass · error

missing hostname in database URI

Error message

missing hostname in database URI

What it means

loadDatabase parsed the database URI but u.Hostname() returned empty: the URI has a scheme and username yet no host component (e.g. "postgres://user@/dbname"). The graph database server address is mandatory, so the guard rejects the URI before any connection is attempted.

Source

Thrown at config/graphdb.go:119

	return nil
}

func (c *Config) loadDatabase(dbURI string) error {
	u, err := url.Parse(dbURI)
	if err != nil {
		return err
	}
	// Check for valid scheme (database type)
	if u.Scheme == "" {
		return fmt.Errorf("missing scheme in database URI")
	}
	// Check for non-empty username
	if u.User == nil || u.User.Username() == "" {
		return fmt.Errorf("missing username in database URI")
	}
	// Check for reachable hostname
	if u.Hostname() == "" {
		return fmt.Errorf("missing hostname in database URI")
	}

	dbName := ""
	// Only get the database name if it's not empty or a single slash
	if u.Path != "" && u.Path != "/" {
		dbName = strings.TrimPrefix(u.Path, "/")
	}

	db := &Database{
		Primary:  true, // Set as primary, because it wouldn't be there otherwise.
		URL:      dbURI,
		System:   u.Scheme,
		Username: u.User.Username(),
		DBName:   dbName,
		Host:     u.Hostname(), // Hostname without port
		Port:     u.Port(),     // Get port
	}

View on GitHub (pinned to 79299dce87)

Solutions

1. Add the host to the URI: neo4j://user:pass@localhost:7687/db.
2. If using a socket/file-based DB, use the scheme/host syntax the driver actually supports instead of a bare path.
3. Print the parsed URI parts (scheme, host, path) in a quick script to confirm what the config resolves to.

Example fix

// before
"database": "neo4j://user:pass@/mydb"
// after
"database": "neo4j://user:pass@localhost:7687/mydb"

u, _ := url.Parse(dbURI)
if u.Hostname() == "" {
    return errors.New("database URI must include a hostname")
}

if err := loadDatabase(uri); err != nil {
    if strings.Contains(err.Error(), "missing hostname") {
        return fmt.Errorf("check host portion of %q", uri)
    }
}

When it happens

Trigger: A configured URI missing the host, e.g. 'neo4j://user:pass@/db' or 'neo4j://user:pass@' reaching loadDatabase.

Common situations: Copy-paste mistakes that delete the host portion; a config template with a placeholder host that was never filled in; Unix-socket style URIs that this parser does not understand.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

Related errors

• missing scheme in database URI
• missing username in database URI
• unable to parse database URI query parameters: %v
• resolver entry %v is not a string
• brute forcing cannot be performed without DNS resolution

AI-assisted analysis of owasp-amass/amass@79299dce87 (2026-09-06). Data as JSON: /api/errors/01f510c7f25e8186. Report an issue: GitHub.