The vulnerability arises from the use of Python's eval() to process mathematical expressions submitted over the MCP protocol. Because the input is not sanitized, an attacker can embed arbitrary Python code, which the server executes with the privileges of the process. This flaw allows an attacker to run any command, read or modify data, or take full control of the underlying system. The weakness corresponds to CWE‑94 (Code Injection) and the insecure use of eval reflects CWE‑1427.

All releases of MCP Calculate Server prior to version 0.1.1 are affected. The product, developed by 611711Dark, is a mathematical calculation service that relies on SymPy. Users running any version before the security update are vulnerable.

The CVSS score of 9.8 indicates critical severity, and the lack of an EPSS assessment suggests no publicly reported exploitation yet, but the flaw remains exploitable by anyone who can connect to the MCP service. The vulnerability is listed as not in the CISA KEV catalog, but its high impact and ease of exploitation mean the recommended posture is to apply the fix immediately. The likely attack path involves sending a malicious mathematical expression through the MCP protocol, which is executed directly by eval(), giving the attacker remote code execution on the host.