Keras vulnerable to CVE-2025-1550 bypass via reuse of internal functionality

Summary

It is possible to bypass the mitigation introduced in response to CVE-2025-1550, when an untrusted Keras v3 model is loaded, even when “safe_mode” is enabled, by crafting malicious arguments to built-in Keras modules.

The vulnerability is exploitable on the default configuration and does not depend on user input (just requires an untrusted model to be loaded).

Impact

Details

Keras’ safe_mode flag is designed to disallow unsafe lambda deserialization - specifically by rejecting any arbitrary embedded Python code, marked by the “lambda” class name. https://github.com/keras-team/keras/blob/v3.8.0/keras/src/saving/serialization_lib.py#L641 -

if config["class_name"] == "__lambda__":
        if safe_mode:
            raise ValueError(
                "Requested the deserialization of a `lambda` object. "
                "This carries a potential risk of arbitrary code execution "
                "and thus it is disallowed by default. If you trust the "
                "source of the saved model, you can pass `safe_mode=False` to "
                "the loading function in order to allow `lambda` loading, "
                "or call `keras.config.enable_unsafe_deserialization()`."
            )

A fix to the vulnerability, allowing deserialization of the object only from internal Keras modules, was introduced in the commit .