CVE-2021-37667: Reference binding to nullptr in unicode encoding in TensorFlow
First published: Thu Aug 12 2021(Updated: )
### Impact An attacker can cause undefined behavior via binding a reference to null pointer in `tf.raw_ops.UnicodeEncode`: ```python import tensorflow as tf from tensorflow.python.ops import gen_string_ops gen_string_ops.unicode_encode( input_values=[], input_splits=[], output_encoding='UTF-8', errors='ignore', replacement_char='a') ``` The [implementation](https://github.com/tensorflow/tensorflow/blob/460e000de3a83278fb00b61a16d161b1964f15f4/tensorflow/core/kernels/unicode_ops.cc#L533-L539) reads the first dimension of the `input_splits` tensor before validating that this tensor is not empty: ```cc const Tensor& input_splits = context->input(1); const auto input_splits_flat = input_splits.flat<SPLITS_TYPE>(); TensorShape output_shape({input_splits.dim_size(0) - 1}); ``` ### Patches We have patched the issue in GitHub commit [2e0ee46f1a47675152d3d865797a18358881d7a6](https://github.com/tensorflow/tensorflow/commit/2e0ee46f1a47675152d3d865797a18358881d7a6). 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 members of the Aivul Team from Qihoo 360.
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Google TensorFlow | >=2.3.0<2.3.4 | |
| Google TensorFlow | >=2.4.0<2.4.3 | |
| Google TensorFlow | =2.5.0 | |
| Google TensorFlow | =2.6.0-rc0 | |
| Google TensorFlow | =2.6.0-rc1 | |
| Google TensorFlow | =2.6.0-rc2 | |
| pip/tensorflow-gpu | =2.5.0 | 2.5.1 |
| pip/tensorflow-gpu | >=2.4.0<2.4.3 | 2.4.3 |
| pip/tensorflow-gpu | <2.3.4 | 2.3.4 |
| pip/tensorflow-cpu | =2.5.0 | 2.5.1 |
| pip/tensorflow-cpu | >=2.4.0<2.4.3 | 2.4.3 |
| pip/tensorflow-cpu | <2.3.4 | 2.3.4 |
| pip/tensorflow | =2.5.0 | 2.5.1 |
| pip/tensorflow | >=2.4.0<2.4.3 | 2.4.3 |
| pip/tensorflow | <2.3.4 | 2.3.4 |
| >=2.3.0<2.3.4 | ||
| >=2.4.0<2.4.3 | ||
| =2.5.0 | ||
| =2.6.0-rc0 | ||
| =2.6.0-rc1 | ||
| =2.6.0-rc2 |
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Reference Links
- https://github.com/tensorflow/tensorflow/commit/2e0ee46f1a47675152d3d865797a18358881d7a6
- https://github.com/tensorflow/tensorflow/security/advisories/GHSA-w74j-v8xh-3w5h
- https://nvd.nist.gov/vuln/detail/CVE-2021-37667
- https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-580.yaml
- https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-778.yaml
- https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-289.yaml
- https://github.com/advisories/GHSA-w74j-v8xh-3w5h (Advisory)
Frequently Asked Questions
What is CVE-2021-37667?
CVE-2021-37667 is a vulnerability in TensorFlow that allows an attacker to cause undefined behavior.
How does the vulnerability in TensorFlow occur?
The vulnerability in TensorFlow occurs when an attacker binds a reference to a null pointer in `tf.raw_ops.UnicodeEncode`.
What is the severity of CVE-2021-37667?
CVE-2021-37667 has a severity rating of 7.8 (high).
Which versions of TensorFlow are affected by CVE-2021-37667?
Versions 2.3.0 to 2.3.4, 2.4.0 to 2.4.3, 2.5.0, and 2.6.0-rc0 to 2.6.0-rc2 of TensorFlow are affected by CVE-2021-37667.
How can I fix the vulnerability in TensorFlow?
To fix the vulnerability in TensorFlow, update to a version that is not affected by CVE-2021-37667.
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