Actual behavior
kaniko unpacks build context archives using filepath.Join(dest, cleanedName) without enforcing that the final path stays within dest. A tar entry like ../outside.txt escapes the extraction root and writes files outside the destination directory. In environments with registry authentication, or when running via tini, this can be chained with external helper binaries to achieve code execution within the executor process.

Mitigation:
You can strip external helper binaries from the image, you don't need them for registry authentication, even for ECR and others