# Security Findings Report - MCP Shamash Security Server
**Project**: MCP Shamash Security Server
**Assessment Type**: Internal Security Review
**Scope**: Sprint 6 Implementation
**Assessment Date**: 2025-09-02
**Status**: Active Findings Requiring Resolution
## Executive Summary
During the Sprint 6 implementation review, a comprehensive security assessment was conducted on the MCP Shamash security server codebase. This assessment identified **1 critical vulnerability** and **2 medium-risk issues** that require immediate attention before production deployment.
**Risk Level Summary**:
- 🔴 **Critical**: 1 finding (ReDoS vulnerability)
- 🟡 **Medium**: 2 findings (Input validation, Information disclosure)
- 🟢 **Low**: 0 findings
- ℹ️ **Informational**: 0 findings
## Critical Findings
### 🔴 CRITICAL: Regular Expression Denial of Service (ReDoS) Vulnerability
**Finding ID**: SHAMASH-CRIT-001
**Severity**: Critical
**CVSS Score**: 7.5 (High)
**Status**: ⚠️ OPEN - Requires immediate fix
**Location**:
- File: `src/rules/custom-rule-engine.ts`
- Line: 309
- Function: `applyRuleToContent()`
**Vulnerable Code**:
```typescript
const regex = new RegExp(rule.pattern, 'gi'); // User input directly used in regex
let match;
while ((match = regex.exec(content)) !== null) {
// Processing loop - vulnerable to ReDoS
}
```
**Vulnerability Description**:
The custom rule engine allows users to provide regex patterns that are directly compiled and executed without validation for complexity or safety. This creates a Regular Expression Denial of Service (ReDoS) vulnerability where malicious patterns can cause exponential backtracking, leading to CPU exhaustion and service denial.
**Attack Vector**:
1. Attacker creates malicious custom rule with catastrophic backtracking pattern
2. Rule is executed against file content during scanning
3. Regex engine enters exponential backtracking loop
4. Service becomes unresponsive due to CPU exhaustion
**Example Malicious Pattern**:
```regex
(a+)+b
^(a+)+$
(a|a)*b
```
**Impact Assessment**:
- **Availability**: High - Can cause complete service denial
- **Performance**: High - Exponential CPU usage growth
- **Resource Consumption**: High - Memory and CPU exhaustion
- **Service Reliability**: High - Affects all scanning operations
**Proof of Concept**:
```typescript
// Malicious rule that would cause ReDoS
const maliciousRule = {
pattern: "(a+)+b", // Catastrophic backtracking pattern
// ... other rule properties
};
// When scanning content like "aaaaaaaaaaaaaaaaaaaaX" (no 'b' at end)
// The regex engine will try all possible combinations exponentially
```
**Risk Factors**:
- User-controlled regex patterns
- No complexity validation
- No timeout mechanisms
- Unbounded execution time
- Public API exposure via MCP
**Remediation Priority**: IMMEDIATE (Pre-production blocker)
**Recommended Fixes**:
1. **Input Validation** (Primary):
```typescript
private validateRegexSafety(pattern: string): boolean {
// Check for common ReDoS patterns
const dangerousPatterns = [
/\(.*\+.*\)\+/, // (x+)+ patterns
/\(.*\*.*\)\*/, // (x*)* patterns
/\(.*\|.*\)\*/, // (x|y)* patterns with overlap
/\(.*\+.*\)\{/, // (x+){n,m} patterns
];
return !dangerousPatterns.some(p => p.test(pattern));
}
```
2. **Timeout Protection** (Secondary):
```typescript
private applyRuleWithTimeout(rule: CustomRule, content: string, timeoutMs: number = 1000) {
return new Promise((resolve, reject) => {
const timer = setTimeout(() => {
reject(new Error('Regex execution timeout'));
}, timeoutMs);
try {
const result = this.applyRuleToContent(rule, content, lines, filePath);
clearTimeout(timer);
resolve(result);
} catch (error) {
clearTimeout(timer);
reject(error);
}
});
}
```
3. **Safe Regex Library** (Recommended):
```typescript
import { safe } from 'safe-regex';
private validatePattern(pattern: string): boolean {
return safe(pattern);
}
```
## Medium Risk Findings
### 🟡 MEDIUM: Insufficient Input Validation
**Finding ID**: SHAMASH-MED-001
**Severity**: Medium
**CVSS Score**: 5.3 (Medium)
**Status**: ⚠️ OPEN
**Locations**:
- `src/core/server.ts` - Multiple tool handlers
- `src/rules/custom-rule-engine.ts` - Rule validation
**Issue Description**:
Several user input fields lack comprehensive validation, potentially allowing malformed or malicious data to be processed by the system.
**Specific Concerns**:
1. **File Path Traversal**: Limited validation of file paths in scan requests
2. **Rule Name Injection**: Custom rule names not sanitized for special characters
3. **URL Validation**: Basic URL validation in pentest scanner
4. **Pattern Length Limits**: No maximum length limits on custom rule patterns
**Impact**:
- Path traversal attacks
- Log injection
- Resource exhaustion
- System information disclosure
**Recommended Fixes**:
```typescript
// Enhanced path validation
private validatePath(path: string): boolean {
const normalizedPath = require('path').normalize(path);
return !normalizedPath.includes('..') &&
!normalizedPath.startsWith('/') &&
normalizedPath.length <= 500;
}
// Rule name sanitization
private sanitizeRuleName(name: string): string {
return name.replace(/[<>:"/\\|?*\x00-\x1f]/g, '').substring(0, 100);
}
```
### 🟡 MEDIUM: Information Disclosure in Error Messages
**Finding ID**: SHAMASH-MED-002
**Severity**: Medium
**CVSS Score**: 4.3 (Medium)
**Status**: ⚠️ OPEN
**Locations**:
- `src/core/server.ts` - Error handling in tool methods
- `src/scanners/*.ts` - Scanner error messages
**Issue Description**:
Error messages may expose sensitive information about the system architecture, file system structure, or internal implementation details that could aid attackers.
**Examples of Information Leakage**:
```typescript
// Problematic error message
throw new Error(`Scanner failed: ${result.stderr}`); // Exposes scanner internals
// Improved error message
throw new Error('Scanner execution failed'); // Generic, safe message
```
**Impact**:
- System reconnaissance
- Architecture fingerprinting
- Attack surface mapping
- Credential leakage in stack traces
**Recommended Fixes**:
1. **Generic Error Messages**: Use sanitized, generic error messages for user-facing responses
2. **Detailed Logging**: Log detailed errors securely for administrators
3. **Error Categorization**: Implement error codes instead of descriptive messages
## Security Controls Assessment
### ✅ Effective Security Controls
1. **Boundary Enforcement**: Strong project scope validation prevents path traversal
2. **Container Isolation**: Proper Docker containerization with resource limits
3. **Resource Limits**: CPU, memory, and process limits prevent resource exhaustion
4. **Audit Logging**: Comprehensive operation logging for security monitoring
5. **Token Management**: Proper budget management prevents token abuse
### ⚠️ Security Controls Requiring Enhancement
1. **Input Validation**: Needs strengthening across all user inputs
2. **Error Handling**: Requires sanitization to prevent information leakage
3. **Regex Validation**: Critical need for ReDoS protection
4. **Rate Limiting**: No protection against request flooding
5. **Authentication**: No authentication mechanism implemented
## Compliance Impact
### Affected Compliance Frameworks
1. **OWASP Top 10 2021**:
- A03: Injection (ReDoS is a form of injection attack)
- A05: Security Misconfiguration (Inadequate input validation)
- A09: Security Logging and Monitoring Failures (Information disclosure)
2. **CIS Controls v8**:
- Control 11: Data Recovery (Availability impact from ReDoS)
- Control 16: Network Monitoring and Defense
3. **NIST Cybersecurity Framework**:
- PR.DS-1: Data-at-rest protection
- DE.CM-1: Network monitoring
- RS.MI-3: Incident response procedures
## Risk Assessment Matrix
| Finding | Likelihood | Impact | Overall Risk | Priority |
|---------|------------|---------|--------------|----------|
| ReDoS Vulnerability | High | High | Critical | P0 - Immediate |
| Input Validation | Medium | Medium | Medium | P1 - High |
| Information Disclosure | Low | Medium | Medium | P2 - Medium |
## Remediation Timeline
### Phase 1: Critical Fixes (Week 1)
- **Day 1-2**: Fix ReDoS vulnerability in custom rule engine
- **Day 3-4**: Implement comprehensive testing for ReDoS protection
- **Day 5**: Security validation and testing
### Phase 2: Medium Risk Fixes (Week 2)
- **Day 1-3**: Enhance input validation across all components
- **Day 4-5**: Implement sanitized error handling
- **Day 6-7**: Testing and validation
### Phase 3: Security Hardening (Week 3)
- **Additional security controls implementation**
- **Comprehensive security testing**
- **Documentation updates**
## Testing Recommendations
### Security Testing Required
1. **ReDoS Testing**:
- Test malicious regex patterns
- Validate timeout mechanisms
- Performance testing under attack conditions
2. **Input Validation Testing**:
- Boundary testing for all inputs
- Malicious input injection testing
- Path traversal attempt validation
3. **Error Handling Testing**:
- Information leakage validation
- Error message sanitization testing
## Conclusion
The MCP Shamash security server demonstrates strong foundational security with effective boundary enforcement and container isolation. However, the identified ReDoS vulnerability presents a critical security risk that must be resolved before production deployment.
**Immediate Actions Required**:
1. Fix ReDoS vulnerability (Critical Priority)
2. Enhance input validation (High Priority)
3. Sanitize error messages (Medium Priority)
**Production Readiness**: The system requires security fixes before deployment but has a solid security foundation that can be enhanced to meet production security requirements.
---
**Assessment Completed**: 2025-09-02
**Next Review**: After remediation implementation
**Security Status**: ⚠️ FINDINGS REQUIRE RESOLUTION
**Production Deployment**: ❌ BLOCKED until critical fix implemented
