# CVE-2016-9243: PYSEC-2017-8 - HKDF in cryptography before 1.5.2 returns an empty byte-string if used with a length less than algorithm.digest_size.

Source: https://junglewise.ai/threats/cve-2016-9243-improper-input-validation-in-cryptography  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-03-27  
License: CC BY 4.0 with a link back

CVE-2016-9243 · Severity: low · CVSS 3 · Published 2017-03-27

HKDF in cryptography before 1.5.2 returns an empty byte-string if used with a length less than algorithm.digest_size.

Technologies: [cryptography (PyPI)](https://junglewise.ai/threats/technologies/cryptography). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2016-9243 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-9243 being exploited in the wild.

**How severe is CVE-2016-9243?** Low severity, with a CVSS score of 3, published 27 March 2017.

**Which products and versions are affected?** cryptography (PyPI) ECOSYSTEM:introduced=0,fixed=1.5.3, GIT:introduced=0,fixed=b924696b2e8731f39696584d12cceeb3aeb2d874|ECOSYSTEM:introduced=0,fixed=1.5.3.

**Is there a fix for CVE-2016-9243?** Yes. cryptography (PyPI): upgrade to 1.5.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2016-9243?** Check whether you run cryptography (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- cryptography (PyPI): upgrade to 1.5.3 or later

  ```sh
  pip install "cryptography>=1.5.3"
  ```


## Affected products

- cryptography (PyPI) ECOSYSTEM:introduced=0,fixed=1.5.3, GIT:introduced=0,fixed=b924696b2e8731f39696584d12cceeb3aeb2d874|ECOSYSTEM:introduced=0,fixed=1.5.3

## Identifiers

- CVE-2016-9243
- GHSA-q3cj-2r34-2cwc
- PYSEC-2017-8

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