CVE-2026-55558 aiosmtplib: STARTTLS response injection

aiosmtplib is an asynchronous SMTP client for use with asyncio. Prior to 5.1.2, SMTPProtocol.starttls in src/aiosmtplib/protocol.py consumes the server's 220 response and starts the TLS handshake without clearing SMTPProtocol.buffer. An active network attacker can place attacker-chosen SMTP...