MCP Server for Splunk

# Security Vulnerability Analysis: SVD-2025-1210 ## Executive Summary **Date**: December 5, 2025 **Severity**: MEDIUM (CVSS 5.4) **Status**: ✅ **ADDRESSED** - Different architecture than affected Splunk MCP Server ## Splunk Advisory Details - **Advisory ID**: SVD-2025-1210 - **CVE ID**: CVE-2025-20381 - **Published**: December 3, 2025 - **CVSS v3.1 Score**: 5.4 (Medium) - **CVSS Vector**: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L - **CWE**: CWE-863 (Incorrect Authorization) ### Vulnerability Description In Splunk MCP Server app versions below 0.2.4, a user with access to the "run_splunk_query" MCP tool could bypass SPL command allowlist controls by embedding SPL commands as sub-searches (using square brackets `[]`), leading to unauthorized actions beyond the intended MCP restrictions. ## Our Architecture - Key Difference **This project (deslicer/mcp-for-splunk) uses a fundamentally different security model than the affected Splunk MCP Server app.** ### Splunk MCP Server (Affected) - Implements its own SPL command allowlist - Subsearches bypass the allowlist → **VULNERABLE** ### Our Implementation (deslicer/mcp-for-splunk) - **Does NOT implement command allowlists** that can be bypassed - **Relies on Splunk RBAC** for all authorization - Users authenticate with their own Splunk credentials - Splunk Enterprise enforces index access and command permissions - **Subsearches execute with the authenticated user's permissions** → No bypass possible ## Security Model ### How We Handle Authorization 1. **User Authentication**: Each MCP request uses the user's Splunk credentials 2. **Splunk RBAC**: Splunk Enterprise validates all queries against user's roles 3. **Index Access**: Controlled by Splunk roles, not MCP layer 4. **Command Permissions**: Controlled by Splunk capabilities, not MCP layer ### Why CVE-2025-20381 Doesn't Apply The vulnerability exists when: 1. MCP layer has an allowlist that restricts commands 2. Subsearches bypass that MCP-layer allowlist 3. Splunk executes commands the MCP intended to block In our architecture: 1. We don't have an MCP-layer allowlist to bypass 2. All authorization is delegated to Splunk RBAC 3. Subsearches run with the same permissions as the parent query ## What We DO Protect Against Our `src/core/security.py` module blocks: | Command | Reason | |---------|--------| | `collect` | Data exfiltration to new indexes | | `outputlookup` | Writing data to lookups | | `outputcsv` | Writing data to CSV files | | `delete` | Data deletion | | `sendemail` | External communication | | `script` | External script execution | | `run` | External command execution | These are blocked at the MCP layer as **defense in depth** - they represent data modification or external execution that should require explicit user action, not automated agent execution. ### Complexity Limits - **Max query length**: 50,000 characters (prevent DoS) - **Max pipeline depth**: 50 pipes (prevent resource exhaustion) ## Recommendations for Operators 1. **Use dedicated Splunk accounts** for MCP access with appropriate role restrictions 2. **Configure Splunk roles** to limit index access based on user needs 3. **Enable Splunk audit logging** to monitor MCP-initiated searches 4. **Review Splunk capabilities** assigned to MCP user roles ## Security Scanning This PR adds comprehensive security scanning: - **Bandit**: Python SAST scanning - **Semgrep**: Multi-language SAST with security rules - **Trivy**: Dependency vulnerability scanning - **Gitleaks**: Secret detection - **CodeQL**: Advanced security analysis ## References - [Splunk Advisory SVD-2025-1210](https://advisory.splunk.com/advisories/SVD-2025-1210) - [CVE-2025-20381](https://nvd.nist.gov/vuln/detail/CVE-2025-20381) - [Splunk RBAC Documentation](https://docs.splunk.com/Documentation/Splunk/latest/Security/Aboutusersandroles) --- **Last Updated**: December 8, 2025 **Status**: ✅ ANALYZED - Not affected due to architectural differences