High 7.5Published Mar 27, 2017

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

Updated under an hour ago (Nov 2, 2026, 12:10 AM ET)

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It affects cryptography.io cryptography and 2 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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

CVSS: 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Modified
Record last updated: Jun 16, 2026
First seen by InfoSec Signals: Nov 1, 2026

Affected products

Affected products

cryptography.io cryptography cryptography.io:cryptography	through 1.5.2	NVD
fedoraproject fedora fedoraproject:fedora	23; 24; 25	NVD
canonical ubuntu_linux canonical:ubuntu_linux	16.04; 16.10	NVD

References

References

http://www.openwall.com/lists/oss-security/2016/11/09/2	mailing-list, patch, vdb-entry
http://www.securityfocus.com/bid/94216	broken-link, third-party-advisory, vdb-entry
http://www.ubuntu.com/usn/USN-3138-1	third-party-advisory
https://cryptography.io/en/latest/changelog	release-notes, third-party-advisory
https://github.com/pyca/cryptography/commit/b924696b2e8731f39696584d12cceeb3aeb2d874	patch, third-party-advisory
https://github.com/pyca/cryptography/issues/3211	issue-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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.