# AC-4(19)_validation-of-metadata

> When transferring information between different security domains, implement [organization-defined] on metadata.

- Skill: `cyberstrikeus/ac-4-19-validation-of-metadata` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/ac-4-19-validation-of-metadata`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/ac-4-19-validation-of-metadata/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/ac-4-19-validation-of-metadata

---


# AC-4(19) Validation of Metadata

> **Enhancement of:** AC-4

## High-Level Description

**Family:** Access Control (AC)
**Framework:** NIST SP 800-53 Rev 5

All information (including metadata and the data to which the metadata applies) is subject to filtering and inspection. Some organizations distinguish between metadata and data payloads (i.e., only the data to which the metadata is bound). Other organizations do not make such distinctions and consider metadata and the data to which the metadata applies to be part of the payload.

## What to Check

- [ ] Verify AC-4(19) Validation of Metadata is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for AC-4(19)
- [ ] Verify enhancement builds upon base control AC-4

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for AC-4(19) 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

| Tool            | Purpose                                | Usage                      |
| --------------- | -------------------------------------- | -------------------------- |
| cloud-audit-mcp | Check IAM policies and access controls | `cloud_audit_iam_policies` |
| hackbrowser | Test web application access controls   | `hackbrowser`        |

## Remediation Guide

### Control Statement

When transferring information between different security domains, implement [organization-defined] on metadata.

### Implementation Guidance

All information (including metadata and the data to which the metadata applies) is subject to filtering and inspection. Some organizations distinguish between metadata and data payloads (i.e., only the data to which the metadata is bound). Other organizations do not make such distinctions and consider metadata and the data to which the metadata applies to be part of the payload.

## Risk Assessment

| Finding                                         | Severity | Impact                    |
| ----------------------------------------------- | -------- | ------------------------- |
| AC-4(19) Validation of Metadata not implemented | High     | Access Control            |
| AC-4(19) partially implemented                  | Medium   | Incomplete Access Control |

## CWE Categories

| CWE ID  | Title                   |
| ------- | ----------------------- |
| CWE-284 | Improper Access Control |

## References

- [NIST SP 800-53 Rev 5 - AC-4(19)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=ac-4.19)
- [NIST SP 800-53A Rev 5 (Assessment Procedures)](https://csrc.nist.gov/pubs/sp/800/53/a/r5/final)
- [NIST SP 800-53 Rev 5 Full Catalog](https://csrc.nist.gov/pubs/sp/800/53/r5/upd1/final)

## Checklist

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