kobako Sandbox Escape: guest eval reaches host RCE via method_missing → public_send (any bound Service)

Date Aug 18, 2026
Type Vendor advisory
Signal High-risk advisory
Vendor / Product RubyGems · kobako
CVE CVE-2026-55107
High-risk advisory CVE-2026-55107

Summary

kobako Sandbox Escape: guest eval reaches host RCE via method_missing → public_send (any bound Service)

Why it matters

GitHub has published a reviewed security advisory for kobako. Prioritize it with other application dependency updates.

Operator check

Check whether kobako is present in application dependency manifests, lockfiles, or build images. Review the GitHub advisory and upgrade to a patched version where available.

Sources

PatchBrief uses public sources. It does not scan environments, verify exposure, or replace vendor guidance.