---
id: CVE-2026-74900
aliases:
  - PYSEC-2026-3772
  - GHSA-p3gq-pcg9-qvfv
title: >-
  openssl_encrypt versions before 1.4.0 contain a critical vulnerability in
  pqc.py where KEM decapsulation failures silently fall back to s…
summary: >-
  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 p…
severity: none
vendor: openssl-encrypt
product: openssl-encrypt
ecosystem: pip
affected:
  - openssl-encrypt < 1.4.0
patched:
  - openssl-encrypt 1.4.0
published: '2026-08-17'
updated: '2026-09-02'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/PYSEC-2026-3772'
references:
  - url: >-
      https://github.com/jahlives/openssl_encrypt/security/advisories/GHSA-p3gq-pcg9-qvfv
  - url: >-
      https://www.vulncheck.com/advisories/openssl-encrypt-before-weak-shared-secret-via-pqc-simulation-mode
tags:
  - osv
  - pip
epss: 0.00559
epssPercentile: 0.44232
ingestedAt: '2026-09-02T19:31:25.909Z'
---

## Overview

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.

## Affected packages

- `openssl-encrypt < 1.4.0`

## Remediation

Upgrade to a patched release:

- `openssl-encrypt 1.4.0`