asteval is a Python expression evaluator designed for restricted execution. Prior to 1.0.9, in asteval/astutils.py, the default Interpreter with numpy enabled exposes a ctypes type and permits from_address memory access. safe_getattr blocks the ctypes module but not reachable ctypes type objects, while attribute assignments use unfiltered setattr instead of safe_setattr. An attacker-controlled expression can derive an address with id, read memory through from_address, and write through an attribute assignment.
The expression can read or corrupt arbitrary process memory, escape the intended sandbox, execute code, disclose secrets, or crash the host process. This issue is fixed in version 1.0.9.
Attack Parameters
Attack Vector
Local
Requires local access
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
References 4
https://github.com/lmfit/asteval/commit/a3e56e7f8ed567a4817684d94213b290359077b4
security-advisories@github.com
https://github.com/lmfit/asteval/pull/153
security-advisories@github.com
https://github.com/lmfit/asteval/releases/tag/1.0.9
security-advisories@github.com
https://github.com/lmfit/asteval/security/advisories/GHSA-9w56-46f6-3qhx
security-advisories@github.com