CVE-2026-55546

CVE-2026-55546 · QWED-MCP: Unsafe SymPy `parse_expr()` Remote Code Execution via Unsanitized Math Expression Input

This page contains facts from public vulnerability sources. Check the original advisory before updating.

QWED-MCP is a deterministic verification gateway for MCP. Prior to 0.2.1, verify_math_expression() in src/qwed_mcp/engines/math_engine.py passes attacker-controlled expression and claimed_result strings directly to SymPy's parse_expr() after only normalizing caret syntax to Python exponent syntax, without restricting global_dict, removing Python built-ins, or validating the expression AST. Because parse_expr() calls Python's eval() with built-ins available, an attacker who can cause a downstream caller to pass untrusted input to this public library function can use Python import functionality to execute arbitrary operating-system commands as the qwed-mcp process user, read or modify accessible data, exfiltrate process secrets, or reach internal services. The default MCP tool registry does not expose verify_math_expression(), so exploitation requires a downstream integration that invokes the library API with attacker-controlled input. This issue is fixed in version 0.2.1.

CVSS 9.8 · Critical · EPSS 0.7% · Fix available

Published

2026-08-25T15:25:34.759Z

Updated

2026-08-25T18:26:44.049Z

Stack: python

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