How severe is CVE-2026-55107?

CVE-2026-55107 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-55107 being actively exploited?

It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.

How do I fix CVE-2026-55107?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-55107 published?

CVE-2026-55107 was published on 2026-09-30.

CVE-2026-55107

CVE-2026-55107 is a critical-severity vulnerability with a CVSS 3.x base score of 10.0. The underlying weakness is classified as CWE-94.

Key facts

Severity: Critical (CVSS 3.x base score 10.0)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-94
Published: 2026-09-30
Last modified: 2026-09-30

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.

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.
How severe is CVE-2026-55107?: CVE-2026-55107 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-55107 being actively exploited?: It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.
How do I fix CVE-2026-55107?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-55107 published?: CVE-2026-55107 was published on 2026-09-30.

References

Other CWE-94 (Code Injection) vulnerabilities

CVE-2026-96349 — Critical (CVSS 10.0): Unauthenticated Remote Code Execution (RCE) in SiteSkite <= 2.1.8 versions.
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CVE-2026-75721 — Critical (CVSS 10.0): Adobe Campaign Classic (ACC) is affected by an Improper Control of Generation of Code ('Code Injection') vulnerability…
CVE-2026-75703 — Critical (CVSS 10.0): Adobe Campaign Classic (ACC) is affected by an Improper Control of Generation of Code ('Code Injection') vulnerability…
CVE-2026-75699 — Critical (CVSS 10.0): Adobe Campaign Classic (ACC) is affected by an Improper Control of Generation of Code ('Code Injection') vulnerability…

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