---
title: "CVE-2026-55107: Kobako Ruby gem - Remote Code Execution"
description: "Kobako Ruby gem >= 0.1.0 and < 0.9.1 contains a remote code execution caused by sandbox escape allowing guest mruby scripts to execute arbitrary Ruby in the host process, letting attackers fully escape the sandbox, exploit requires running untrusted mruby scripts."
url: https://panop.io/threat-heartbeat/CVE-2026-55107/
---

# CVE-2026-55107 Kobako Ruby gem - Remote Code Execution

Kobako Ruby gem >= 0.1.0 and < 0.9.1 contains a remote code execution caused by sandbox escape allowing guest mruby scripts to execute arbitrary Ruby in the host process, letting attackers fully escape the sandbox, exploit requires running untrusted mruby scripts.

CVSS base score 10.0 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.80% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-55107)

## Details

Type

Remote Code Execution

Impact

Remote Code Execution

CVSS vector

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

Published

30 September 2026

Updated

15 October 2026

Weakness

[CWE-94](https://cwe.mitre.org/data/definitions/94.html)

## Vendor fix

Upgrade to version 0.9.1 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-55107](https://nvd.nist.gov/vuln/detail/CVE-2026-55107)
- [https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3](https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3)
- [https://github.com/elct9620/kobako/releases/tag/v0.9.1](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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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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