GHSA-vp47-9734-prjw — ASTEVAL Allows Malicious Tampering of Exposed AST Nodes Leads to Sandbox Escape

Affected: PyPI: asteval

### Summary If an attacker can control the input to the asteval library, they can bypass its safety restrictions and execute arbitrary Python code within the application's context.

### Details The vulnerability is rooted in how `asteval` performs attribute access verification. In particular, the [`on_attribute`](https://github.com/lmfit/asteval/blob/8d7326df8015cf6a57506b1c2c167a1c3763e090/asteval/asteval.py#L565) node handler prevents access to attributes that are either present in the `UNSAFE_ATTRS` list or are formed by names starting and ending with `__`, as shown in the code snippet below:

```py def on_attribute(self, node): # ('value', 'attr', 'ctx') """Extract attribute."""

ctx = node.ctx.__class__ if ctx == ast.Store: msg = "attribute for storage: shouldn't be here!" self.raise_exception(node, exc=RuntimeError, msg=msg)

sym = self.run(node.value) if ctx == ast.Del: return delattr(sym, node.attr) # unsafe = (node.attr in UNSAFE_ATTRS or (node.attr.startswith('__') and node.attr.endswith('__'))) if not unsafe: for dtype, attrlist in UNSAFE_ATTRS_DTYPES.items(): unsafe = isinstance(sym, dtype) and node.attr in attrlist if unsafe: break if unsafe: msg = f"no safe attribute '{node.attr}' for {repr(sym)}" self.raise_exception(node, exc=AttributeError, m…

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GHSA-vp47-9734-prjw — ASTEVAL Allows Malicious Tampering of Exposed AST Nodes Leads to Sandbox Escape