[ CVE-2026-55107 · Published 30 Sep 2026 ]
Vulnerability in elct9620 kobako
CVSS 10.0
EPSS <1%No fix listed yet
[ Why it matters ]Priority signals
- Public proof-of-concept exploit exists (CISA SSVC)
- Critical severity: CVSS 10.0
[ Description ]Official description
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.
[ Fixes ]Fixes and patches
No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.