Arbitrary Command Execution in MCP Server by Sonirico

CVE-2026-55581

What is CVE-2026-55581?

The mcp-shell server, which allows for the secure execution of shell commands, had a significant vulnerability prior to version 0.6.0. The default configuration in security.yaml permitted /bin/bash in the list of allowed executables. However, due to insufficient validation in security.go, an attacker could exploit the shell_exec tool by passing a command as '/bin/bash -c ', which would bypass the intended constraints. This exploited command would be executed as mcpuser, allowing for unauthorized actions. The issue has been addressed in the 0.6.0 release, effectively closing this security hole.

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