EUVD-2026-63376

aiosmtplib: STARTTLS response injection...

GHSA-VXJ7-4XRP-5VR4 aiosmtplib: STARTTLS response injection

Impact When a connection is upgraded with STARTTLS, aiosmtplib reads the server's 220 go-ahead reply and immediately performs the TLS handshake without discarding any data still sitting in the receive buffer. Bytes the protocol read off the plaintext socket before the handshake survive across the...

Linux Distros Unpatched Vulnerability : CVE-2026-55558

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available. - 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...

CVE-2026-55558

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...

DEBIAN-CVE-2026-55558

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...

UBUNTU-CVE-2026-55558

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...

CVE-2026-55558

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...

CVE-2026-55558

CVE-2026-55558 affects aiosmtplib , an asynchronous SMTP client for Python's asyncio, in versions prior to 5.1.2 . The vulnerability resides in SMTPProtocol.start_tls (src/aiosmtplib/protocol.py), which consumes the server's 220 response and initiates the TLS handshake without clearing SMTPProtoc...

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...

PT-2026-79027

Name of the Vulnerable Software and Affected Versions aiosmtplib versions prior to 5.1.2 Description The SMTPProtocol.start tls function in src/aiosmtplib/protocol.py fails to clear the SMTPProtocol. buffer after consuming the server's 220 response and initiating the TLS handshake. A network...

DEBIAN-CVE-2026-53533

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...

CVE-2026-53533

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...

CVE-2026-53533

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...

UBUNTU-CVE-2026-53533

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...

CVE-2026-53533

aiosmtplib's SMTP.mail(), SMTP.rcpt(), SMTP.vrfy(), and SMTP.expn() methods transmit caller-supplied addresses without filtering CR/LF bytes, allowing SMTP command injection (CWE-93/CWE-77) when attacker-influenced addresses are passed. This enables desynchronization, client hangs, or arbitrary m...

CVE-2026-53533 aiosmtplib: SMTP command injection via CR/LF in sender/recipient address

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...

CVE-2026-53533 aiosmtplib: SMTP command injection via CR/LF in sender/recipient address

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...

aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address

Summaryaiosmtplib's SMTP.mail, SMTP.rcpt, SMTP.vrfy and SMTP.expn send the caller-supplied email address to the server without rejecting embedded CR/LF \r\n bytes. An address that contains a CR/LF is written verbatim onto the SMTP control connection, so the bytes after the CRLF are framed by the...

PYSEC-2026-2338 aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address

Summary aiosmtplib's SMTP.mail, SMTP.rcpt, SMTP.vrfy and SMTP.expn send the caller-supplied email address to the server without rejecting embedded CR/LF \r\n bytes. An address that contains a CR/LF is written verbatim onto the SMTP control connection, so the bytes after the CRLF are framed by the...

GHSA-V3Q9-HJ7J-63HQ aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address

Summary aiosmtplib's SMTP.mail, SMTP.rcpt, SMTP.vrfy and SMTP.expn send the caller-supplied email address to the server without rejecting embedded CR/LF \r\n bytes. An address that contains a CR/LF is written verbatim onto the SMTP control connection, so the bytes after the CRLF are framed by the...