Vulnerability Discussion

A common vulnerability of applications is unpredictable behavior when invalid inputs are received. This requirement guards against adverse or unintended system behavior caused by invalid inputs, where information system responses to the invalid input may be disruptive or cause the system to fail into an unsafe state.

The behavior will be derived from the organizational and system requirements and includes, but is not limited to, notification of the appropriate personnel, creating an audit record, and rejecting invalid input.

Check

Verify the API provides input validation.

Review the API documentation and interview the API administrator.
Review the API's input handling mechanisms at all exposed endpoints.

Identify all points where user input is accepted, including query parameters, headers, body content, and path variables.

Verify that input validation is implemented to enforce expected formats, data types, ranges, and lengths.

Ensure validation occurs on the server side, regardless of any client-side checks.

Check for validation against known-safe patterns or whitelists (e.g., regex, enumerated values) and proper rejection of malformed or unexpected input.

If input validation is missing, insufficient, or only enforced on the client side, this is a finding.is is a finding.

Fix

Follow best practice when accepting user input and verify all input is validated before the API processes the input.

Remediate identified vulnerabilities and obtain documented risk acceptance for those issues that cannot be remediated immediately.