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Developer finds RCE vulnerability in SymPy's parse_expr function

A developer discovered a critical security vulnerability in the `sympy.parse_expr` function, which could allow arbitrary code execution if not properly secured. The function, by default, utilizes Python's `eval()`, inheriting built-in functions like `os.system` that can be triggered by malicious input disguised as mathematical formulas. To mitigate this, the developer implemented an Abstract Syntax Tree (AST) validation layer that pre-filters potentially dangerous constructs before `sympy` processes the input, ensuring only safe mathematical operations are allowed. AI

Summary written by gemini-2.5-flash-lite from 1 source. How we write summaries →

IMPACT Highlights the critical need for secure input parsing when integrating LLMs with code execution environments.

RANK_REASON Discovery of a security vulnerability in a specific software function.

Read on dev.to — MCP tag →

COVERAGE [1]

  1. dev.to — MCP tag TIER_1 · kyb8801 ·

    sympy.parse_expr will run os.system if you let it. Here's the AST gate that stopped me from shipping the RCE.

    <h1> sympy.parse_expr will run os.system if you let it. Here's the AST gate that stopped me from shipping the RCE. </h1> <p>I was building an MCP server that accepts a measurement formula as a string from an LLM, parses it with sympy, and evaluates it via Monte Carlo. Five minute…