openssl_encrypt before 1.4.0 Weak Key Derivation via HKDF

published 2026-08-17 2 mo ago modified 2026-10-01 38 d ago also GHSA-j9mh-57cc-665x , PYSEC-2026-3765 , EUVD-2026-60108

cvss: 9.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits: 0; none known

openssl_encrypt versions before 1.4.0 use HKDF with no salt and static info parameter in key normalization functions, reducing entropy extraction and determinism. Attackers can exploit predictable key derivation with identical inputs to weaken cryptographic security against multi-target attacks.

Patch / fix

fixed in 2

pypi openssl-encrypt 1.4.0
jahlives openssl_encrypt 1.4.0

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 2 mo ago (2026-08-17)

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	9.3	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA	4.0	9.3	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem	package	affected	fixed in
pypi	openssl-encrypt	<1.4.0	1.4.0

Affected products

jahlives openssl_encrypt

Classification

Weakness

CWE-326 Inadequate Encryption Strength

References

github.com /jahlives/openssl_encrypt/security/advisories/GHSA-j9mh-57cc-665x
vendor-advisory, mitigation, advisory
vulncheck.com /advisories/openssl-encrypt-before-weak-key-derivation-via-hkdf
third-party-advisory, advisory

Sources

Fencer Vulns 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.

Summary