Heap buffer overflow in `RaggedBinCount`

### Impact If the `splits` argument of `RaggedBincount` does not specify a valid [`SparseTensor`](https://www.tensorflow.org/api_docs/python/tf/sparse/SparseTensor), then an attacker can trigger a heap buffer overflow: ```python import tensorflow as tf tf.raw_ops.RaggedBincount(splits=[0], values=[1,1,1,1,1], size=5, weights=[1,2,3,4], binary_output=False) ``` This will cause a read from outside the bounds of the `splits` tensor buffer in the [implementation of the `RaggedBincount` op](https://github.com/tensorflow/tensorflow/blob/8b677d79167799f71c42fd3fa074476e0295413a/tensorflow/core/kernels/bincount_op.cc#L430-L433): ```cc for (int idx = 0; idx < num_values; ++idx) { while (idx >= splits(batch_idx)) { batch_idx++; } ... } ``` Before the `for` loop, `batch_idx` is set to 0. The user controls the `splits` array, making it contain only one element, 0. Thus, the code in the `while` loop would increment `batch_idx` and then try to read `splits(1)`, which is outside of bounds. ### Patches We have patched the issue in GitHub commit [eebb96c2830d48597d055d247c0e9aebaea94cd5](https://github.com/tensorflow/tensorflow/commit/eebb96c2830d48597d055d247c0e9aebaea94cd5). The fix will be included in TensorFlow 2.5.0. We will also cherrypick this commit on TensorFlow 2.4.2 and TensorFlow 2.3.3, as these are also affected. ### 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.

CVSS 3.1

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

Severity from

GitHub (reviewed advisory)

Weakness

CWE-120, CWE-787

Also known as

BIT-tensorflow-2021-29512, CVE-2021-29512, PYSEC-2021-149, PYSEC-2021-440, PYSEC-2021-638

• github.com/tensorflow/tensorflow/security/advisories/GHSA-4278-2v5v-65r4
• nvd.nist.gov/vuln/detail/CVE-2021-29512
• github.com/tensorflow/tensorflow/commit/eebb96c2830d48597d055d247c0e9aebaea94cd5
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-440.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-638.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-149.yaml