---
id: CVE-2021-37678
aliases:
  - GHSA-r6jx-9g48-2r5r
  - BIT-tensorflow-2021-37678
  - PYSEC-2021-300
  - PYSEC-2021-591
  - PYSEC-2021-789
title: Arbitrary code execution due to YAML deserialization
summary: Arbitrary code execution due to YAML deserialization
severity: critical
cvss: 9.3
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H'
vendor: tensorflow
product: tensorflow
ecosystem: pip
affected:
  - tensorflow < 2.3.4
  - 'tensorflow >= 2.4.0, < 2.4.3'
  - 'tensorflow >= 2.5.0, < 2.5.1'
  - tensorflow-cpu < 2.3.4
  - 'tensorflow-cpu >= 2.4.0, < 2.4.3'
  - 'tensorflow-cpu >= 2.5.0, < 2.5.1'
  - tensorflow-gpu < 2.3.4
  - 'tensorflow-gpu >= 2.4.0, < 2.4.3'
  - 'tensorflow-gpu >= 2.5.0, < 2.5.1'
patched:
  - tensorflow 2.3.4
  - tensorflow 2.4.3
  - tensorflow 2.5.1
  - tensorflow-cpu 2.3.4
  - tensorflow-cpu 2.4.3
  - tensorflow-cpu 2.5.1
  - tensorflow-gpu 2.3.4
  - tensorflow-gpu 2.4.3
  - tensorflow-gpu 2.5.1
published: '2021-08-25'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-r6jx-9g48-2r5r'
references:
  - url: >-
      https://github.com/tensorflow/tensorflow/security/advisories/GHSA-r6jx-9g48-2r5r
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-37678'
  - url: >-
      https://github.com/tensorflow/tensorflow/commit/1df5a69e9f1a18a937e7907223066e606bf466b9
  - url: >-
      https://github.com/tensorflow/tensorflow/commit/23d6383eb6c14084a8fc3bdf164043b974818012
  - url: >-
      https://github.com/tensorflow/tensorflow/commit/8e47a685785bef8f81bcb996048921dfde08a9ab
  - url: >-
      https://github.com/tensorflow/tensorflow/commit/a09ab4e77afdcc6e1e045c9d41d5edab63aafc1a
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow-cpu/PYSEC-2021-591.yaml
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow-gpu/PYSEC-2021-789.yaml
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/tensorflow/PYSEC-2021-300.yaml
  - url: 'https://github.com/tensorflow/tensorflow'
tags:
  - osv
  - pip
  - exploit-available
epss: 0.00447
epssPercentile: 0.36256
ingestedAt: '2026-07-08T18:25:52.658Z'
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/fran-CICS/ExploitTensorflowCVE-2021-37678'
  checkedAt: '2026-09-26T09:05:26.943Z'
exploitAvailable: true
---

## Overview

### Impact
TensorFlow and Keras can be tricked to perform arbitrary code execution when deserializing a Keras model from YAML format.

```python
from tensorflow.keras import models

payload = '''
!!python/object/new:type
args: ['z', !!python/tuple [], {'extend': !!python/name:exec }]
listitems: "__import__('os').system('cat /etc/passwd')"
'''
  
models.model_from_yaml(payload)
```
  
The [implementation](https://github.com/tensorflow/tensorflow/blob/460e000de3a83278fb00b61a16d161b1964f15f4/tensorflow/python/keras/saving/model_config.py#L66-L104) uses `yaml.unsafe_load` which can perform arbitrary code execution on the input.

### Patches
Given that YAML format support requires a significant amount of work, we have removed it for now.

We have patched the issue in GitHub commit [23d6383eb6c14084a8fc3bdf164043b974818012](https://github.com/tensorflow/tensorflow/commit/23d6383eb6c14084a8fc3bdf164043b974818012).

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 Arjun Shibu.

## Affected packages

- `tensorflow < 2.3.4`
- `tensorflow >= 2.4.0, < 2.4.3`
- `tensorflow >= 2.5.0, < 2.5.1`
- `tensorflow-cpu < 2.3.4`
- `tensorflow-cpu >= 2.4.0, < 2.4.3`
- `tensorflow-cpu >= 2.5.0, < 2.5.1`
- `tensorflow-gpu < 2.3.4`
- `tensorflow-gpu >= 2.4.0, < 2.4.3`
- `tensorflow-gpu >= 2.5.0, < 2.5.1`

## Remediation

Upgrade to a patched release:

- `tensorflow 2.3.4`
- `tensorflow 2.4.3`
- `tensorflow 2.5.1`
- `tensorflow-cpu 2.3.4`
- `tensorflow-cpu 2.4.3`
- `tensorflow-cpu 2.5.1`
- `tensorflow-gpu 2.3.4`
- `tensorflow-gpu 2.4.3`
- `tensorflow-gpu 2.5.1`