CVE-2026-55107 Details
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.
A vulnerability in the Kobako Ruby gem, affecting versions 0.1.0 prior to 0.9.1, allows guest mruby scripts to execute arbitrary Ruby code in the host process, completely escaping the intended sandbox. This issue arises because the transport dispatcher forwards guest-supplied method names to 'public_send' on bound Service objects without proper restrictions. As a result, a guest can access private Kernel methods, leading to remote code execution on the host.
Users are advised to upgrade to Kobako version 0.9.1, where this vulnerability has been patched. The updated version includes a method allowlist that blocks access to ambient reflection methods, preventing the exploitation of this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 30, 2026CISA-ADP
Assessed Sep 30, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h | CISA-ADP | AdvisoryRemedyVendor |
| https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3 | [email protected] | Source CodeVendor |
| https://github.com/elct9620/kobako/releases/tag/v0.9.1 | [email protected] | Release NotesVendor |
| https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-470 | Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') | [email protected] |
| CWE-94 | Improper Control of Generation of Code ('Code Injection') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Kobako | >= 0.1.0, <= 0.9.0 (semver) |
CPE
Remediation
| |
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 30, 2026 | CVE Modified | CISA-ADP |
| Sep 30, 2026 | New CVE Received | [email protected] |