{"cve":"CVE-2026-55107","nvd":{"published":"2026-09-30T18:18:37.550","modified":"2026-09-30T20:17:32.923","status":"Deferred","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","score":10.0},"cwes":["CWE-94","CWE-470"],"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"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:56:48.555445741+00:00"},"epss":{"cve":"CVE-2026-55107","score":0.00799,"percentile":0.56276,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-7pwq-q9jf-539h","url":"https://osv.dev/vulnerability/GHSA-7pwq-q9jf-539h","summary":"kobako Sandbox Escape: guest eval reaches host RCE via method_missing → public_send (any bound Service)","modified":"2026-08-18T20:26:08.539217Z","packages":[{"ecosystem":"RubyGems","name":"kobako","purl":"pkg:gem/kobako","ranges":[">=0.1.0 <0.9.1"],"fixed":["0.9.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}