GHSA-8m8r-38jm-f355

Summary

When the Pydantic v2 output mode is in use, datamodel-code-generator reads a validators array from each model entry in the --extra-template-data file and synthesises a Pydantic @field_validator(...) decorator from each entry. The field names and the validator mode are interpolated into the decorator call wrapped in unescaped single quotes. A value containing ' breaks out of the string literal, letting an attacker emit an arbitrary positional Python expression into the decorator. The expression is evaluated at class-definition time, i.e. the moment the developer imports the generated module. This is the same trust model as the recently-published GHSA-wjv6-jcfj-mf9r (extras-file comment injection) but the impact is full RCE rather than a docstring leak.

Details

Sink: src/datamodel_code_generator/model/pydantic_v2/base_model.py, _process_validators (lines 405–449, at tag 0.60.1 / commit a321547e):

def _process_validators(self) -> None:
    validators = self.extra_template_data.get("validators")
    if not validators:
        return
    ...
    for validator in validators:
        fields = validator.get("fields") or [validator.get("field")]
        fields = [f for f in fields if f]
        if not fields:
            continue
        function_path: str = validator["function"]
        function_name = function_path.rsplit(".", 1)[-1]
        mode = validator.get("mode", "after")
        fields_str = ", ".join(f"'{f}'" for f in fields)     # (A) UNESCAPED
        ...
        mode_str = f"mode='{mode}'"                          # (B) UNESCAPED
        prepared_validators.append({
            "fields_str": fields_str,
            "mode_str":   mode_str,
            "method_name": method_name,
            "function_name": function_name,
            "mode": mode,
        })
        self._additional_imports.append(Import.from_full_path(function_path))  # (C)

The strings from (A) and (B) flow verbatim into...