Description (CNA)
ASTEVAL is an evaluator of Python expressions and statements. Prior to version 1.0.6, if an attacker can control the input to the `asteval` library, they can bypass asteval's restrictions and execute arbitrary Python code in the context of the application using the library. The vulnerability is rooted in how `asteval` performs handling of `FormattedValue` AST nodes. In particular, the `on_formattedvalue` value uses the dangerous format method of the str class. The code allows an attacker to manipulate the value of the string used in the dangerous call `fmt.format(__fstring__=val)`. This vulnerability can be exploited to access protected attributes by intentionally triggering an `AttributeError` exception. The attacker can then catch the exception and use its `obj` attribute to gain arbitrary access to sensitive or protected object properties. Version 1.0.6 fixes this issue.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| lmfit / asteval | affected < 1.0.6 |
CWE
CWE-134, CWE-749
References
- https://github.com/lmfit/asteval/security/advisories/GHSA-3wwr-3g9f-9gc7
- https://github.com/lmfit/asteval/blob/cfb57f0beebe0dc0520a1fbabc35e66060c7ea71/asteval/asteval.py#L507
- https://lucumr.pocoo.org/2016/12/29/careful-with-str-format
ADP enrichment
No English description supplied.
No references supplied.