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 ↗

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

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

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