FPE in `tf.raw_ops.UnravelIndex`

### Impact An attacker can cause denial of service in applications serving models using `tf.raw_ops.UnravelIndex` by triggering a division by 0: ```python import tensorflow as tf tf.raw_ops.UnravelIndex(indices=-1, dims=[1,0,2]) ``` The [implementation](https://github.com/tensorflow/tensorflow/blob/460e000de3a83278fb00b61a16d161b1964f15f4/tensorflow/core/kernels/unravel_index_op.cc#L36) does not check that the tensor subsumed by `dims` is not empty. Hence, if one element of `dims` is 0, the implementation does a division by 0. ### Patches We have patched the issue in GitHub commit [a776040a5e7ebf76eeb7eb923bf1ae417dd4d233](https://github.com/tensorflow/tensorflow/commit/a776040a5e7ebf76eeb7eb923bf1ae417dd4d233). 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.

CVSS 3.1

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

Severity from

GitHub (reviewed advisory)

Weakness

CWE-369

Also known as

BIT-tensorflow-2021-37668, CVE-2021-37668, PYSEC-2021-290, PYSEC-2021-581, PYSEC-2021-779

• github.com/tensorflow/tensorflow/security/advisories/GHSA-2wmv-37vq-52g5
• nvd.nist.gov/vuln/detail/CVE-2021-37668
• github.com/tensorflow/tensorflow/commit/a776040a5e7ebf76eeb7eb923bf1ae417dd4d233
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-581.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-779.yaml
• github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-290.yaml
• github.com/tensorflow/tensorflow