CVE-2026-55107: Code Injection (CVSS 10)

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.

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CVSS v3.1 Score

10.0

CRITICAL

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

EPSS — Exploit Prediction

0.0080

Probability of exploitation

0.55%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-94 CWE-94

CWE-470 CWE-470

References

Other 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

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 10.0 (CRITICAL).

How severe is CVE-2026-55107? +

CVE-2026-55107 has a CVSS v3.1 score of 10.0 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0080, placing it in the 1th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-55107? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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