Plaintext substitution via uncommitted encrypted data keys

Cryptographic failure in AWS SDK for Ruby 1.207.0 and earlier allows remote authenticated users to alter plaintext via a rogue data key. The S3 Encryption Client accepts an encrypted data key from an instruction file without cryptographically binding it to the ciphertext, so a rogue key makes the same ciphertext decrypt to attacker-chosen content. Exploitation requires both a crafted alternate key that decrypts the existing object and permission to replace its instruction file in the S3 bucket; confidentiality and availability remain unaffected.