CVE-2026-55107

Kobako is a Ruby gem that embeds a Wasm-isolated mruby interpreter inside applications, allowing execution of untrusted Ruby scripts (LLM-generated code, user formulas, student submissions, third-party plugins) in-process without giving them access to host memory, files, network, or credentials. From version 0.1.0 to before version 0.9.1, a guest mruby script running inside the Kobako sandbox can execute arbitrary Ruby in the host process, fully escaping the sandbox. This issue has been patched in version 0.9.1.

• https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3
• https://github.com/elct9620/kobako/releases/tag/v0.9.1
• https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h
• https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h