Unsanitized user input in Access-Control-Allow-Origin

• Rule ID: python_lang_insecure_allow_origin
• Languages: python
• Source: insecure_allow_origin.yml

Description

Using unverified user-defined input to set the Access-Control-Allow-Origin header can result in unauthorized access to sensitive data. This vulnerability exposes your application to potential security risks by allowing attackers to specify origins that can access resources.

Remediations

• Do not use user input to define the Access-Control-Allow-Origin header without validation. This practice can inadvertently grant access to sensitive information.

  self.send_header('Access-Control-Allow-Origin', external_input) # unsafe

• Do validate user input if it must be used to set the Access-Control-Allow-Origin header. Ensure that only trusted origins are allowed by implementing a safelist of approved origins.

    allowed_origins = ['http://www.example.com', 'https://www.secure.example.com']
    
    user_origin = input("Enter origin: ")
    
    if user_origin in allowed_origins:
      self.send_header('Access-Control-Allow-Origin', user_origin)

References

• OWASP Origin & Access-Control-Allow-Origin

Associated CWE

• CWE-346: Origin Validation Error

OWASP Top 10

• A07:2021 - Identification and Authentication Failures

Configuration

To skip this rule during a scan, use the following flag

bearer scan /path/to/your-project/ --skip-rule=python_lang_insecure_allow_origin

To run only this rule during a scan, use the following flag

bearer scan /path/to/your-project/ --only-rule=python_lang_insecure_allow_origin