CVE-2026-74900: openssl_encrypt before 1.4.0 Weak Shared Secret via PQC Simulation Mode
opensslencrypt 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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
openssl_encryptto a version that resolves this vulnerability.Fixed in 1.4.0 - Operational
If you used vulnerable openssl_encrypt versions (before 1.4.0), rotate any keys and re-encrypt data because an attacker with 16 bytes of the private key could compute the shared secret and decrypt all ciphertext.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-74900?
CVE-2026-74900 has a critical severity score of 9.8.
What vulnerability does CVE-2026-74900 describe?
CVE-2026-74900 describes a vulnerability in openssl_encrypt versions before 1.4.0 that allows weak deterministic shared secrets via PQC simulation mode.
How do I fix CVE-2026-74900?
To fix CVE-2026-74900, upgrade to openssl_encrypt version 1.4.0 or later.
What does CVE-2026-74900 affect?
CVE-2026-74900 affects the openssl_encrypt software, specifically versions prior to 1.4.0.
What are the potential risks associated with CVE-2026-74900?
The risks include potential exposure of sensitive data due to predictable shared secrets derived from inadequate key management.