CVE-2026-5504: wolfSSL

Medium severity, CVSS 5.3. EPSS: 0.1% chance of exploitation in the next 30 days.

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Affected products

• wolfSSL wolfSSL: up to and including 5.9.0

Published 2026-04-09. Last modified 2026-06-17.