important · Email — Edge
An on-path attacker can recover plaintext from Cisco-to-Cisco S/MIME traffic.
Affects
Cisco Secure Email gateways running AsyncOS and configured to use S/MIME for gateway-to-gateway email protection
Insufficient ciphertext-integrity validation lets an attacker modify intercepted gateway traffic into a plaintext-recovery path.
Detail and 1 source
Cisco says fixed software is available.