{"id":"CVE-2026-55107","state":"PUBLISHED","title":"Kobako Vulnerable to Sandbox Escape: guest eval reaches host RCE via method_missing → public_send (any bound Service)","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.","publishedAt":"2026-09-30T17:06:00.286Z","updatedAt":"2026-09-30T19:49:04.193Z","severity":{"score":10,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["elct9620 kobako"],"affected":[{"vendor":"elct9620","product":"kobako","versions":[{"version":">= 0.1.0, < 0.9.1","status":"affected"}]}],"references":["https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h","https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3","https://github.com/elct9620/kobako/releases/tag/v0.9.1"],"weaknesses":["CWE-94","CWE-470"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/55xxx/CVE-2026-55107.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-55107","state":"PUBLISHED","datePublished":"2026-09-30T17:06:00.286Z","dateUpdated":"2026-09-30T19:49:04.193Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-16T14:41:54.579Z"},"containers":{"cna":{"title":"Kobako Vulnerable to Sandbox Escape: guest eval reaches host RCE via method_missing → public_send (any bound Service)","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"elct9620","product":"kobako","versions":[{"version":">= 0.1.0, < 0.9.1","status":"affected"}]}],"references":[{"url":"https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h","name":"https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3","name":"https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3","tags":["x_refsource_MISC"]},{"url":"https://github.com/elct9620/kobako/releases/tag/v0.9.1","name":"https://github.com/elct9620/kobako/releases/tag/v0.9.1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":10,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-94","lang":"en","description":"CWE-94: Improper Control of Generation of Code ('Code Injection')","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-470","lang":"en","description":"CWE-470: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-30T17:06:00.286Z"},"source":{"advisory":"GHSA-7pwq-q9jf-539h","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-30T19:48:55.982496Z","id":"CVE-2026-55107","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-30T19:49:04.193Z"}}]}}}