Arbitrary code execution due to YAML deserialization

Impact

TensorFlow and Keras can be tricked to perform arbitrary code execution when deserializing a Keras model from YAML format.

from tensorflow.keras import models

payload = '''
!!python/object/new:type
args: ['z', !!python/tuple [], {'extend': !!python/name:exec }]
listitems: "__import__('os').system('cat /etc/passwd')"
'''
  
models.model_from_yaml(payload)

The implementation uses yaml.unsafe_load which can perform arbitrary code execution on the input.

Patches

Given that YAML format support requires a significant amount of work, we have removed it for now.

We have patched the issue in GitHub commit 23d6383eb6c14084a8fc3bdf164043b974818012.

The fix will be included in TensorFlow 2.6.0. We will also cherrypick this commit on TensorFlow 2.5.1, TensorFlow 2.4.3, and TensorFlow 2.3.4, as these are also affected and still in supported range.

For more information

Please consult our security guide for more information regarding the security model and how to contact us with issues and questions.

Attribution

This vulnerability has been reported by Arjun Shibu.