Fix Improper Error Handling in Sinatra
Improper error handling in Sinatra applications often leads to Information Leakage (CWE-209). By default, Sinatra's development settings or misconfigured production environments leak stack traces, file paths, and database queries to the client. An attacker can leverage this metadata to map the application's internal architecture, identify vulnerable library versions, and craft precise exploits.
The Vulnerable Pattern
require 'sinatra'VULNERABLE: Enabling show_exceptions in production leaks stack traces
set :show_exceptions, true
get ‘/api/data/:id’ do
If ID is not an integer, the DB driver might throw a raw exception
which is then rendered directly to the user.
result = DB.execute(“SELECT * FROM items WHERE id = #{params[:id]}”) result.to_json end
The Secure Implementation
To secure Sinatra, first disable 'show_exceptions' in production to stop the middleware from intercepting exceptions and rendering the 'Cascade' backtrace page. Use the 'error' and 'not_found' blocks to define a global catch-all that returns sanitized, generic messages. Implement local exception handling with 'begin/rescue' or 'halt' for predictable failures. Always log the actual exception object (env['sinatra.error']) to a secure server-side log, but never expose it to the HTTP response.
require 'sinatra' require 'json'configure :production do disable :show_exceptions set :raise_errors, false set :dump_errors, true end
Global error handler for internal server errors
error do content_type :json status 500 { error: ‘Internal Server Error’, reference: env[‘sinatra.error’].object_id }.to_json end
Custom 404 handler
not_found do content_type :json status 404 { error: ‘Resource not found’ }.to_json end
get ‘/api/data/:id’ do begin id = Integer(params[:id]) # Use parameterized queries to prevent SQLi and handle logic result = DB.execute(“SELECT * FROM items WHERE id = ?”, id) halt 404 if result.empty? result.to_json rescue ArgumentError halt 400, { error: ‘Invalid ID format’ }.to_json end end
Your Sinatra API
might be exposed to Improper Error Handling
74% of Sinatra apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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