CVE-2026-107377datamodel-code-generator generates Python data models from schema definitions. From 0.59.0 until 0.81.0, an attacker-controlled Protobuf schema can supply absolute or parent-directory paths captured by WEAK_IMPORT_PATTERN and consumed by _write_missing_weak_imports in src/datamodel_code_generator/parser/protobuf.py. Exploitation requires a victim or automated job to process the attacker-controlled schema with Protobuf input support, which requires the grpcio-tools package. The paths escape the weak_imports temporary directory before protoc runs, allowing creation of directory trees and new files or overwrite of existing writable files with a generated Protobuf syntax declaration. The effect persists when later Protobuf compilation fails. The written content is limited to a proto2 or proto3 syntax declaration, and direct arbitrary code execution has not been demonstrated. This issue is fixed in version 0.81.0.