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CVE-2026-55107— Kobako Vulnerable to Sandbox Escape: guest eval reaches host RCE via method_missing → public_send (any bound Service)

Quick assessment

Affected
elct9620 kobako
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Kobako 是一个 Ruby gem，它在应用程序中嵌入了一个基于 Wasm 隔离的 mruby 解释器，允许在进程内执行不受信任的 Ruby 脚本（例如 LLM 生成的代码、用户公式、学生提交内容或第三方插件），同时防止这些脚本访问宿主机的内存、文件、网络或凭据。在 0.1.0 版本至 0.9.1 之前的版本中，运行在 Kobako 沙箱内的 guest mruby 脚本可以在宿主进程中执行任意 Ruby 代码，从而完全逃逸出沙箱。该问题已在 0.9.1 版本中修复。

CVSS 10.0 · Critical

Affected Version Matrix 1

VendorProduct Version RangeStatus
elct9620 kobako >= 0.1.0, < 0.9.1 affected
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I. Basic Information for CVE-2026-55107

Vulnerability Information
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Vulnerability Title
Kobako Vulnerable to Sandbox Escape: guest eval reaches host RCE via method_missing → public_send (any bound Service)
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对生成代码的控制不恰当(代码注入)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
elct9620 kobako >= 0.1.0, < 0.9.1 -

II. Public POCs for CVE-2026-55107

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III. Intelligence Information for CVE-2026-55107

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Patches & Fixes for CVE-2026-55107 (1)

Vendor Advisories for CVE-2026-55107 (1)

Other References for CVE-2026-55107 (1)

IV. Related Vulnerabilities

Same weakness: CWE-94

V. Comments for CVE-2026-55107

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