CVE-2016-9243

Name: CVE-2016-9243
Creator: NVD / NIST
Published: 2017-03-27T17:59:00.46+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 3.40%

Last modified Jun 17, 2026

CVE-2016-9243 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. HKDF in cryptography before 1.5.2 returns an empty byte-string if used with a length less than algorithm.digest_size.. EPSS estimates a 3.40% chance of exploitation in the next 30 days.

Description

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

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

3.40%

87.3th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Cryptography.Io	Cryptography	<= 1.5.2
Fedoraproject	Fedora	23
Fedoraproject	Fedora	24
Fedoraproject	Fedora	25
Canonical	Ubuntu Linux	16.04
Canonical	Ubuntu Linux	16.10

References

http://www.openwall.com/lists/oss-security/2016/11/09/2Mailing List, Patch, VDB Entry
http://www.securityfocus.com/bid/94216Broken Link, Third Party Advisory, VDB Entry
http://www.ubuntu.com/usn/USN-3138-1Third Party Advisory
https://cryptography.io/en/latest/changelogRelease Notes, Third Party Advisory
https://github.com/pyca/cryptography/commit/b924696b2e8731f39696584d12cceeb3aeb2d874Patch, Third Party Advisory
https://github.com/pyca/cryptography/issues/3211Issue Tracking, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5R2ZOBMPWDFFHUZ6QOZZY36A6H5CGJXL/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U23KDR2M2N7W2ZSREG63BVW7D4VC6CIZ/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WQ5G7KHKZC4SI23JE7277KZXM57GEQKT/Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2016/11/09/2Mailing List, Patch, VDB Entry
http://www.securityfocus.com/bid/94216Broken Link, Third Party Advisory, VDB Entry
http://www.ubuntu.com/usn/USN-3138-1Third Party Advisory
https://cryptography.io/en/latest/changelogRelease Notes, Third Party Advisory
https://github.com/pyca/cryptography/commit/b924696b2e8731f39696584d12cceeb3aeb2d874Patch, Third Party Advisory
https://github.com/pyca/cryptography/issues/3211Issue Tracking, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5R2ZOBMPWDFFHUZ6QOZZY36A6H5CGJXL/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U23KDR2M2N7W2ZSREG63BVW7D4VC6CIZ/Mailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WQ5G7KHKZC4SI23JE7277KZXM57GEQKT/Mailing List, Third Party Advisory

Timeline

Published: Mar 27, 2017
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2016-9243?

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

How severe is CVE-2016-9243?

CVE-2016-9243 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 3.40% probability of exploitation in the next 30 days.

How do I fix CVE-2016-9243?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

Related CVEs from 2016

View all 2016CVEs →

Are you affected by CVE-2016-9243?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST