Amazon S3 Encryption Client for .NET: Critical Padding Oracle Vulnerability

Amazon S3 Encryption Client for .NET has a nasty security flaw (CVE-2026-110310) that lets attackers downgrade your encryption padding to the vulnerable PKCS#1 v1.5 scheme. If someone can read your encrypted S3 objects, they could exploit a padding oracle attack to recover your RSA keys and decrypt everything. Action required: update immediately if you're running versions 2.1.0+, 3.0.0-3.2.1, or 4.0.0-4.0.2.