SI-10_information-input-validation

SI-10 Information Input Validation

High-Level Description

Family: System and Information Integrity (SI) Framework: NIST SP 800-53 Rev 5

Checking the valid syntax and semantics of system inputs—including character set, length, numerical range, and acceptable values—verifies that inputs match specified definitions for format and content. For example, if the organization specifies that numerical values between 1-100 are the only acceptable inputs for a field in a given application, inputs of "387," "abc," or "%K%" are invalid inputs and are not accepted as input to the system. Valid inputs are likely to vary from field to field within a software application. Applications typically follow well-defined protocols that use structured messages (i.e., commands or queries) to communicate between software modules or system components. Structured messages can contain raw or unstructured data interspersed with metadata or control information. If software applications use attacker-supplied inputs to construct structured messages without properly encoding such messages, then the attacker could insert malicious commands or special characters that can cause the data to be interpreted as control information or metadata. Consequently, the module or component that receives the corrupted output will perform the wrong operations or otherwise interpret the data incorrectly. Prescreening inputs prior to passing them to interpreters prevents the content from being unintentionally interpreted as commands. Input validation ensures accurate and correct inputs and prevents attacks such as cross-site scripting and a variety of injection attacks.

What to Check

• Verify SI-10 Information Input Validation is documented in SSP
• Confirm control is operating effectively
• Review evidence of continuous monitoring for SI-10

How to Test

Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for SI-10 implementation details. Verify the organization has documented how this control is satisfied.

Step 2: Validate Implementation

# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly

# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null

Step 3: Test Operating Effectiveness

Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.

Tools

Remediation Guide

Control Statement

Check the validity of the following information inputs: [organization-defined].

Implementation Guidance

Checking the valid syntax and semantics of system inputs—including character set, length, numerical range, and acceptable values—verifies that inputs match specified definitions for format and content. For example, if the organization specifies that numerical values between 1-100 are the only acceptable inputs for a field in a given application, inputs of "387," "abc," or "%K%" are invalid inputs and are not accepted as input to the system. Valid inputs are likely to vary from field to field within a software application. Applications typically follow well-defined protocols that use structured messages (i.e., commands or queries) to communicate between software modules or system components. Structured messages can contain raw or unstructured data interspersed with metadata or control information. If software applications use attacker-supplied inputs to construct structured messages without properly encoding such messages, then the attacker could insert malicious commands or special characters that can cause the data to be interpreted as control information or metadata. Consequently, the module or component that receives the corrupted output will perform the wrong operations or otherwise interpret the data incorrectly. Prescreening inputs prior to passing them to interpreters prevents the content from being unintentionally interpreted as commands. Input validation ensures accurate and correct inputs and prevents attacks such as cross-site scripting and a variety of injection attacks.

Risk Assessment

CWE Categories

References

• NIST SP 800-53 Rev 5 - SI-10
• NIST SP 800-53A Rev 5 (Assessment Procedures)
• NIST SP 800-53 Rev 5 Full Catalog

Checklist

• Control documented in SSP
• Implementation evidence collected
• Operating effectiveness validated
• Continuous monitoring in place
• Related controls (none) reviewed