Codebase Impact Analysis

Determines whether a Go codebase is impacted by a specific CVE by applying multiple analysis methods with increasing confidence, collecting evidence, and assigning a risk level.

When to Use This Skill

Use this skill when:

• A CVE profile has been gathered (from the cve-intelligence-gathering skill)
• You need to determine if the current Go project is affected
• You need to assign a risk level with supporting evidence

Prerequisites

Required Tools (validated in Phase 0 of parent command)

• go toolchain with go.mod in workspace root
• govulncheck: go install golang.org/x/vuln/cmd/govulncheck@latest
• callgraph: go install golang.org/x/tools/cmd/callgraph@latest
• digraph: go install golang.org/x/tools/cmd/digraph@latest

Required Inputs

From Phase 1 (CVE Intelligence Gathering skill):

• CVE ID
• Affected package/module name(s)
• Vulnerable version range
• Fixed version (if available)
• Vulnerable function signatures (if known)

From Parent Command:

• --algo preference for call graph analysis (default: vta)

Implementation Steps

Step 1: Identify Go Module Dependencies

# Parse dependencies from go.mod
go list -m all

# Get detailed dependency info
go list -m -json all

• Read go.mod from workspace root
• Parse direct and indirect dependencies
• Extract module versions

Step 2: Cross-Reference Vulnerable Packages

Apply the following methods in order. Each provides increasing confidence.

Method 1: Dependency Matching

• Compare CVE-affected packages with go.mod dependencies
• Check if affected package versions are in use
• Account for version ranges and semantic versioning

# Check if vulnerable package is a dependency
go list -m <vulnerable-package>

Decision Point:

• IF package NOT in dependencies → Skip to risk assignment (likely LOW RISK)
• IF package found → Continue to Method 2

Method 2: Go Vulnerability Scanner

# Run official Go vulnerability scanner
govulncheck ./...

• Parse output for CVE matches
• Check if vulnerable symbols are reported as called

Decision Point:

• IF govulncheck confirms vulnerability → Strong evidence for HIGH RISK
• IF govulncheck does not find it → Continue to Method 3 (CVE may not be in Go vulndb yet)

Method 3: Direct Dependency Check

# Verify package is included (directly or transitively)
go list -mod=mod <vulnerable-package>

Note: Package presence alone doesn't prove vulnerable functions are called.

Method 4: Source Code Analysis

• Search for import statements of vulnerable packages in source code
• Use grep/codebase_search to find package usage
• Search for vulnerable function/method names in codebase
• Identify actual code paths that use vulnerable functions
• Check if vulnerable functions are called in reachable code

Method 5: Call Graph Reachability Analysis (Highest Confidence)

Delegate to the call-graph-analysis skill.

• Pass: --algo preference from user, vulnerable function signature, package path
• Receive: Risk level, call chain, evidence files
• Only run if: Codebase compiles successfully and highest confidence assessment is needed

Method 6: Configuration and Context Analysis

• Review if vulnerable features are actually enabled
• Check if vulnerable code paths are behind feature flags
• Verify if inputs can reach vulnerable functions
• Consider security controls (input validation, sandboxing)

Confidence Levels

Each method provides increasing confidence:

1. Basic Presence (Low) — Package in go.mod (Method 1, 3)
2. Import & Version Analysis (Medium) — Package imported, version in vulnerable range, function names found (Method 4)
3. Vulnerability Scanner (Medium-High) — govulncheck confirms reachable vulnerable symbols (Method 2)
4. Call Graph Reachability (Highest) — Proven execution path from entry point to vulnerable function (Method 5)
5. Context Analysis — Mitigating or aggravating factors (Method 6)

Use multiple methods. Confidence determination should be data-driven, not formula-based.

Step 3: Build Evidence Package

Collect evidence from all methods used:

• Dependency Evidence: go.mod entries, go list output, version info
• Static Code Evidence: File paths, line numbers, code snippets showing usage
• Reachability Evidence: Call graph output, execution paths, DOT visualization (saved to .work/compliance/analyze-cve/{CVE-ID}/callgraph.svg)
• Scanner Evidence: govulncheck output, vulnerability findings
• Mitigation Factors: Input validation, disabled features, feature flags, security controls

Step 4: Assign Risk Level

Evaluate all evidence and assign a risk level. The determination should be data-driven, not formula-based.

HIGH RISK:

• Call graph shows reachable path to vulnerable function, OR govulncheck confirms vulnerability

MEDIUM RISK:

• Package + vulnerable version found in dependencies, usage evidence present but reachability not fully proven

LOW RISK:

• Package not in dependencies, OR version not in vulnerable range, OR no reachable path found

NEEDS REVIEW:

• Conflicting signals, incomplete analysis, or low-confidence evidence

Return Value

Return structured result to parent command:

{
  "skill": "codebase-impact-analysis",
  "status": "success",
  "risk_level": "<HIGH|MEDIUM|LOW|NEEDS_REVIEW>",
  "methods_used": ["dependency_matching", "govulncheck", "direct_dependency_check", "source_code_analysis", "call_graph", "context_analysis"],
  "evidence": {
    "dependency": {
      "package_found": true,
      "current_version": "<version>",
      "dependency_type": "<direct|indirect>",
      "in_vulnerable_range": true
    },
    "govulncheck": {
      "ran": true,
      "cve_found": true,
      "vulnerable_symbols_called": true
    },
    "call_graph": {
      "ran": true,
      "algorithm": "<vta|rta|cha|static>",
      "reachable_from_main": true,
      "call_chain": "main -> handler -> parse -> VULN",
      "evidence_files": ["callgraph.dot", "callgraph.svg"]
    },
    "source_analysis": {
      "import_found": true,
      "function_usage_found": true,
      "files": ["<file1>:<line>", "<file2>:<line>"]
    },
    "mitigation_factors": []
  },
  "confidence_assessment": {
    "level": "<HIGH|MEDIUM|LOW>",
    "methods_count": 4,
    "gaps": ["<any gaps in analysis>"]
  }
}

Error Handling

Build Failures

• IF project doesn't compile → Note limitation, skip call graph analysis, rely on other methods

Missing CVE in govulncheck Database

• IF govulncheck doesn't know about this CVE → Continue with other methods, note gap

Large Codebases

• IF call graph times out → Follow fallback strategy in call-graph-analysis skill (algorithm fallback, then scope narrowing)

Incomplete CVE Information

• IF vulnerable function signature unknown → Skip call graph method, rely on dependency and scanner methods

Integration with Parent Command

This skill is called from Phase 2 of the /compliance:analyze-cve command.

Input: CVE profile from Phase 1, --algo preference from user Output: Risk level, evidence package, confidence assessment Next: Parent command uses risk level to decide whether to generate report and proceed to remediation