CVE-2026-102734: asteval sandbox escape: arbitrary native memory read/write via numpy ctypes in default asteval Interpreter

Vulnerability summary

CVE-2026-102734 is a medium (CVSS 5.5) Protection Mechanism Failure vulnerability in lmfit asteval. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.3% of scored vulnerabilities.

Timeline

1. 13-10-2026
   PublishedVulnerability first disclosed.
2. 13-10-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-693Protection Mechanism FailureThe product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.
• CWE-749Exposed Dangerous Method or FunctionThe product provides an Applications Programming Interface (API) or similar interface for interaction with external actors, but the interface includes a dangerous method or function that is not properly restricted.
• CWE-913Improper Control of Dynamically-Managed Code ResourcesThe product does not properly restrict reading from or writing to dynamically-managed code resources such as variables, objects, classes, attributes, functions, or executable instructions or statements.