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.

CVSS 3.1

10.0CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS

0.8% chance of exploitation in the next 30 days; higher than 56% of CVEs (scores of 2026-10-25)

CWEs

CWE-94, CWE-470

Published

2026-09-30

Modified

2026-09-30

Record from

the NVD, synced 2026-10-19

Packages (OSV)

References

• 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

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