CVE-2026-74900 openssl_encrypt before 1.4.0 Weak Shared Secret via PQC Simulation Mode

Critical 9.3 Published 17 Aug 2026 Updated 1 Oct 2026

Attackers can decrypt ciphertext by exploiting a silent fallback to deterministic shared secret generation in the openssl_encrypt library.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-74900?

CVE-2026-74900 is a critical vulnerability in Jahlives Openssl Encrypt, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

openssl_encrypt versions before 1.4.0 contain a critical vulnerability in pqc.py where KEM decapsulation failures silently fall back to simulation mode, generating a deterministic shared secret from only 16 bytes of the private key and publicly available encapsulated key data. Attackers who obtain 16 bytes of the private key can compute the shared secret and decrypt all ciphertext, as the fallback triggers on any KEM failure without raising an error.

Weakness: CWE-391

Which versions are affected by CVE-2026-74900?

1 open source package ship an affected version, including openssl-encrypt. It affects 1 product.

Package	Affected	Fixed in
`openssl-encrypt` PyPI	All versions	`1.4.0`

Products include Jahlives Openssl Encrypt.

How do I fix CVE-2026-74900?

Upgrade openssl-encrypt to 1.4.0 or later.

Is CVE-2026-74900 being exploited?

There is no known exploitation of CVE-2026-74900 in the wild and no public exploit code.

All Jahlives Openssl Encrypt vulnerabilities

Sources

Also known as GHSA-7qj7-jv8m-rfjw, GHSA-p3gq-pcg9-qvfv, PYSEC-2026-3772.