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Fencer Intel
high 7.5

CVE-2016-9243 json

Improper input validation in cryptography

published 2017-03-27 9 y ago modified 2026-06-17 4 mo ago also GHSA-q3cj-2r34-2cwc , PYSEC-2017-8 , EUVD-2017-0020

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.5%
EPSS 3.5% chance of exploitation in 30 days, percentile 89%
public exploits
0
none known

Summary

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

Patch / fix

  • pypi cryptography 1.5.3
  • python-cryptography Debian 14, Debian 13, Debian 12 1.5.3-1

debian advisories DEBIAN-CVE-2016-9243

  • python-cryptography Ubuntu 16.04 LTS 1.2.3-1ubuntu0.1

ubuntu advisories UBUNTU-CVE-2016-9243

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-9243 updated cvss 4.8

python-cryptography: HKDF might return an empty byte-string

  • Red Hat Enterprise Linux OpenStack Platform 7 (Kilo) python-cryptography Red Hat OpenStack Platform 8 (Liberty) python-cryptography Red Hat OpenStack Platform 9 (Mitaka) python-cryptography Red Hat OpenStack Platform 10 (Newton) python-cryptography
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux 7 python-cryptography, python2-cryptography
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.46% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N
GitHub 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
pypi cryptography
<1.5.3
1.5.3

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.