Threat Intelligence Database

CVE-2026-90467 is a vulnerability in the aiosmtplib library before version 5.1.3 where improper validation of email addresses allows attackers to inject ESMTP parameters into MAIL FROM and RCPT TO commands. This can enable attackers to forge authenticated identities or manipulate delivery notifications by appending parameters such as AUTH, NOTIFY, or ORCPT. The vulnerability has a medium severity with a CVSS score of 6.3.

CVE-2026-55558 is a vulnerability in aiosmtplib affecting versions prior to 5.1.2 when using STARTTLS. The issue arises because data buffered after the server's 220 go-ahead reply and before the TLS handshake is not discarded, allowing an active man-in-the-middle attacker to inject malicious response lines that are parsed as part of the encrypted session, causing desynchronization of command/response pairs. Implicit TLS connections (use_tls=True) are not affected. A fix is available in version 5.1.2.

aiosmtplib is an asynchronous SMTP client for use with asyncio. Prior to 5.1.1, SMTP.mail(), SMTP.rcpt(), SMTP.vrfy(), and SMTP.expn() send caller-supplied addresses without rejecting embedded CR or LF bytes. Data after the line break is framed as additional standalone SMTP command lines, allowing an attacker who influences an envelope sender or recipient to inject commands such as MAIL FROM, RCPT TO, RSET, DATA, or AUTH. SMTP.sendmail() and SMTP.send() without a Message object pass addresses through the affected methods, while SMTP.send_message() is not affected. Successful injection can desynchronize the command-response pipeline, hang the SMTP instance, or send an arbitrary message without requiring attacker control of the SMTP server. This issue is fixed in version 5.1.1.