/vulnhunter

name: vulnhunter
description: Security vulnerability detection and variant analysis skill. Use when hunting for dangerous APIs, footgun patterns, error-prone configurations, and vulnerability variants across codebases. Combines sharp edges detection with variant hunting methodology.

VulnHunter - Security Vulnerability Detection & Analysis

A comprehensive security audit skill for identifying dangerous APIs, footgun patterns, error-prone configurations, and hunting for vulnerability variants across codebases. Inspired by Trail of Bits' sharp-edges and variant-analysis methodologies.

Overview

VulnHunter combines two powerful security analysis techniques: 1. **Sharp Edges Detection** - Identify error-prone APIs, dangerous defaults, and footgun designs 2. **Variant Analysis** - Find similar vulnerabilities across codebases using pattern-based analysis

When to Use VulnHunter

**Activate this skill when:**

• Conducting security code reviews or audits
• Reviewing third-party dependencies for dangerous patterns
• Hunting for variants of known vulnerabilities
• Assessing API design for security footguns
• Pre-audit reconnaissance of unfamiliar codebases

Sharp Edges Detection

Categories of Sharp Edges

1. Dangerous Default Configurations

Look for configurations that are insecure by default:

- CORS: Access-Control-Allow-Origin: *
- Debug modes enabled in production
- Default credentials or API keys
- Permissive file permissions (777, 666)
- SSL/TLS verification disabled
- Insecure deserialization settings

2. Error-Prone APIs

**Memory Safety:**

// Dangerous: No bounds checking
strcpy(), strcat(), sprintf(), gets()
memcpy() without size validation

// Safer alternatives
strncpy(), strncat(), snprintf(), fgets()
memcpy_s() with explicit size

**Cryptography Footguns:**

- ECB mode encryption
- MD5/SHA1 for security purposes
- Hardcoded IVs or salts
- Custom crypto implementations
- Random without CSPRNG (Math.random for tokens)

**Concurrency Issues:**

- Race conditions in file operations
- Time-of-check to time-of-use (TOCTOU)
- Double-checked locking anti-patterns
- Non-atomic increment/decrement operations

3. Language-Specific Footguns

**JavaScript/TypeScript:**

// Dangerous patterns
eval(), new Function(), setTimeout(string)
innerHTML, outerHTML, document.write()
Object.assign() for deep clone (shallow only!)
== instead of === (type coercion)

**Python:**

# Dangerous patterns
pickle.loads(untrusted)  # RCE vector
yaml.load(untrusted)     # Use safe_load
exec(), eval()
os.system(), subprocess with shell=True

**Rust:**

// Patterns requiring extra scrutiny
unsafe { }
.unwrap() in production code
mem::transmute()
raw pointer dereference

**Solidity/Smart Contracts:**

// High-risk patterns
tx.origin for authentication  // Phishing vulnerable
delegatecall to untrusted     // Storage collision
selfdestruct                  // Permanent destruction
block.timestamp for randomness // Miner manipulable

Sharp Edges Checklist

When reviewing code, systematically check for:

• [ ] **Authentication bypasses** - Missing auth checks, default credentials
• [ ] **Authorization flaws** - Privilege escalation, IDOR patterns
• [ ] **Injection vectors** - SQL, Command, Template, XSS
• [ ] **Cryptographic weaknesses** - Weak algorithms, improper key handling
• [ ] **Resource exhaustion** - Unbounded loops, memory allocation
• [ ] **Race conditions** - TOCTOU, concurrent state modification
• [ ] **Information disclosure** - Verbose errors, debug endpoints
• [ ] **Deserialization** - Untrusted data unmarshaling
• [ ] **Path traversal** - User-controlled file paths
• [ ] **SSRF vectors** - User-controlled URLs, redirects

Variant Analysis

The Variant Hunting Process

1. **Identify the Root Cause** - Understand WHY a vulnerability exists 2. **Extract the Pattern** - What code structure enables it? 3. **Generalize the Pattern** - Create regex/AST patterns 4. **Search Codebase** - Hunt for similar structures 5. **Validate Findings** - Confirm each variant is exploitable

Pattern Extraction Templates

Template 1: Missing Validation Pattern

Original bug: User input flows to SQL query without sanitization
Pattern: [user_input] -> [sink_function] without [validation_function]

Search for:
- Direct database calls with string concatenation
- ORM raw query methods with user parameters
- Similar data flows in adjacent modules

Template 2: Authentication Bypass

Original bug: Endpoint missing auth middleware
Pattern: Route definition without auth decorator/middleware

Search for:
- Routes defined after the vulnerable one
- Similar API patterns in other modules
- Admin/internal endpoints

Template 3: Race Condition

Original bug: Check-then-act without atomicity
Pattern: if (check_condition()) { act_on_condition() }

Search for:
- File existence checks followed by file operations
- Permission checks followed by privileged actions
- Balance checks followed by transfers

Search Strategies

Grep-Based Search

# Find potential SQL injection
grep -rn "execute.*%s" --include="*.py"
grep -rn "query.*\+" --include="*.js"

# Find dangerous deserialize
grep -rn "pickle.loads\|yaml.load\|eval(" --include="*.py"

# Find command injection vectors
grep -rn "os.system\|subprocess.*shell=True" --include="*.py"

Semantic Search (AST-Based)

For more precise matching, use AST-based tools:

• **Semgrep** - Cross-language semantic grep
• **CodeQL** - GitHub's semantic analysis
• **tree-sitter** - Universal parser

Variant Analysis Report Template

## Variant Analysis Report

### Original Finding
- **ID**: FINDING-001
- **Severity**: High
- **Root Cause**: [Description]
- **Affected File**: path/to/file.ext:line

### Pattern Extracted
[Code pattern or regex]

### Variants Discovered

| # | Location | Severity | Status | Notes