The Serverless Framework is a framework for using AWS Lambda and other managed cloud services to build applications. Starting in version 4.29.0 and prior to version 4.29.3, a command injection vulnerability exists in the Serverless Framework's built-in MCP server package (@serverless/mcp). This vulnerability only affects users of the experimental MCP server feature (serverless mcp), which represents less than 0.1% of Serverless Framework users. The core Serverless Framework CLI and deployment functionality are not affected. The vulnerability is caused by the unsanitized use of input parameters within a call to "child_process.exec", enabling an attacker to inject arbitrary system commands. Successful exploitation can lead to remote code execution under the server process's privileges. The server constructs and executes shell commands using unvalidated user input directly within command-line strings. This introduces the possibility of shell metacharacter injection ("|", ">", "&&", etc.). Version 4.29.3 fixes the issue.