---
id: CVE-2021-37686
aliases:
  - GHSA-mhhc-q96p-mfm9
  - BIT-tensorflow-2021-37686
  - PYSEC-2021-308
  - PYSEC-2021-599
  - PYSEC-2021-797
title: Infinite loop in TFLite
summary: Infinite loop in TFLite
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
vendor: tensorflow
product: tensorflow
ecosystem: pip
affected:
  - 'tensorflow >= 2.6.0rc0, < 2.6.0rc2'
  - 'tensorflow-cpu >= 2.6.0rc0, < 2.6.0rc2'
  - 'tensorflow-gpu >= 2.6.0rc0, < 2.6.0rc2'
patched:
  - tensorflow 2.6.0rc2
  - tensorflow-cpu 2.6.0rc2
  - tensorflow-gpu 2.6.0rc2
published: '2021-08-25'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-mhhc-q96p-mfm9'
references:
  - url: >-
      https://github.com/tensorflow/tensorflow/security/advisories/GHSA-mhhc-q96p-mfm9
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-37686'
  - url: >-
      https://github.com/tensorflow/tensorflow/commit/dfa22b348b70bb89d6d6ec0ff53973bacb4f4695
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-599.yaml
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-797.yaml
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-308.yaml
  - url: 'https://github.com/tensorflow/tensorflow'
  - url: 'https://github.com/tensorflow/tensorflow/releases/tag/v2.3.4'
  - url: 'https://github.com/tensorflow/tensorflow/releases/tag/v2.4.3'
  - url: 'https://github.com/tensorflow/tensorflow/releases/tag/v2.5.1'
  - url: 'https://github.com/tensorflow/tensorflow/releases/tag/v2.6.0'
tags:
  - osv
  - pip
epss: 0.00173
epssPercentile: 0.07032
ingestedAt: '2026-07-08T18:25:51.223Z'
---

## Overview

### Impact
The strided slice implementation in TFLite has a logic bug which can allow an attacker to trigger an infinite loop. This arises from newly introduced support for [ellipsis in axis definition](https://github.com/tensorflow/tensorflow/blob/149562d49faa709ea80df1d99fc41d005b81082a/tensorflow/lite/kernels/strided_slice.cc#L103-L122):

```cc
  for (int i = 0; i < effective_dims;) {
    if ((1 << i) & op_context->params->ellipsis_mask) {
      // ...
      int ellipsis_end_idx =
          std::min(i + 1 + num_add_axis + op_context->input_dims - begin_count,
                   effective_dims);
      // ...
      for (; i < ellipsis_end_idx; ++i) {
        // ...
      }
      continue;
    }
    // ...
    ++i;
  }
```

An attacker can craft a model such that `ellipsis_end_idx` is smaller than `i` (e.g., always negative). In this case, the inner loop does not increase `i` and the `continue` statement causes execution to skip over the preincrement at the end of the outer loop.

### Patches
We have patched the issue in GitHub commit [dfa22b348b70bb89d6d6ec0ff53973bacb4f4695](https://github.com/tensorflow/tensorflow/commit/dfa22b348b70bb89d6d6ec0ff53973bacb4f4695).

The fix will be included in TensorFlow 2.6.0. This is the only affected version.

### 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.

## Affected packages

- `tensorflow >= 2.6.0rc0, < 2.6.0rc2`
- `tensorflow-cpu >= 2.6.0rc0, < 2.6.0rc2`
- `tensorflow-gpu >= 2.6.0rc0, < 2.6.0rc2`

## Remediation

Upgrade to a patched release:

- `tensorflow 2.6.0rc2`
- `tensorflow-cpu 2.6.0rc2`
- `tensorflow-gpu 2.6.0rc2`