CyberRota Analysis
AI-GeneratedThe aiosmtplib library, prior to version 5.1.2, is vulnerable due to improper handling of the server's 220 response during the TLS handshake, allowing an active network attacker to inject malicious SMTP response lines. This desynchronization can lead to command and response mismatches within the TLS session, potentially compromising the integrity of email communications. Organizations using aiosmtplib with start_tls enabled should prioritize upgrading to version 5.1.2 to mitigate this risk.
Public Exploit Signal
A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.
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Original NVD Description
aiosmtplib is an asynchronous SMTP client for use with asyncio. Prior to 5.1.2, SMTPProtocol.start_tls 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 response lines after the plaintext 220 response in the same network segment. The method then calls loop.start_tls; those bytes survive the transport upgrade and are parsed as the first response from inside the TLS session, desynchronizing subsequent SMTP command and response pairs. Connections using start_tls=True or opportunistic STARTTLS are affected, while connections using use_tls=True are not. This issue is fixed in version 5.1.2.