What’s Vulnerable › Vulnerabilities

CVE-2016-9243

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2017-03-27 · updated 2026-06-17

Description

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

Affected products

• Canonical Ubuntu Linux: 16.04, 16.10
• pyca cryptography: through 1.5.2
• Fedoraproject Fedora: 23, 24, 25

References

• http://www.openwall.com/lists/oss-security/2016/11/09/2
• http://www.securityfocus.com/bid/94216
• http://www.ubuntu.com/usn/USN-3138-1
• https://cryptography.io/en/latest/changelog
• https://github.com/pyca/cryptography/commit/b924696b2e8731f39696584d12cceeb3aeb2d874
• https://github.com/pyca/cryptography/issues/3211
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5R2ZOBMPWDFFHUZ6QOZZY36A6H5CGJXL/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U23KDR2M2N7W2ZSREG63BVW7D4VC6CIZ/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WQ5G7KHKZC4SI23JE7277KZXM57GEQKT/
• http://www.openwall.com/lists/oss-security/2016/11/09/2
• http://www.securityfocus.com/bid/94216
• http://www.ubuntu.com/usn/USN-3138-1

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