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CVE-2026-53533

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

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 6.9 · Medium · EPSS 0.5% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • aiosmtplib

    Versions
    • < 5.1.1: Affected

    No fix published

  • aiosmtplib Debian:12

    Versions
    • 2.0.0-1
    • 3.0.1-1
    • 3.0.2-1
    • 3.0.2-2
    • 4.0.0-1
    • 4.0.1-1
    • 4.0.1-1~exp1
    • 4.0.2-1
    • 5.0.0-1
    • 5.1.0-1
    • 5.1.0-2
    • 5.1.0-3
    • 5.1.2-1
    • 5.1.3-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • aiosmtplib Debian:13

    Versions
    • 4.0.0-1
    • 4.0.1-1
    • 4.0.1-1~exp1
    • 4.0.2-1
    • 5.0.0-1
    • 5.1.0-1
    • 5.1.0-2
    • 5.1.0-3
    • 5.1.2-1
    • 5.1.3-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • aiosmtplib Debian:14

    Versions
    • 4.0.0-1
    • 4.0.1-1
    • 4.0.1-1~exp1
    • 4.0.2-1
    • 5.0.0-1
    • 5.1.0-1
    • 5.1.0-2
    • 5.1.0-3
    Affected ranges
    • ECOSYSTEM: < 5.1.2-1

    Update to 5.1.2-1

  • aiosmtplib PyPI

    Versions
    • 0.1
    • 0.1.2
    • 0.1.3
    • 0.1.4
    • 0.1.5rc2
    • 0.1.6
    • 0.1.7
    • 1.0.0
    • 1.0.1
    • 1.0.2
    • 1.0.3
    • 1.0.4
    • 1.0.5
    • 1.0.6
    • 1.1.0
    • 1.1.1
    • 1.1.2
    • 1.1.3
    • 1.1.4
    • 1.1.5
    • 1.1.6
    • 1.1.7
    • 1.1b0
    • 2.0.0
    • 2.0.0b0
    • 2.0.0b1
    • 2.0.1
    • 2.0.2
    • 3.0.0
    • 3.0.1
    • 3.0.2
    • 4.0.0
    • 4.0.1
    • 4.0.2
    • 5.0.0
    • 5.1.0
    Affected ranges
    • ECOSYSTEM: < 5.1.1

    Update to 5.1.1

  • aiosmtplib Ubuntu:22.04:LTS

    Versions
    • 1.1.4-1
    • 1.1.4-2
    • 1.1.6-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • aiosmtplib Ubuntu:26.10

    Versions
    • 5.1.0-1
    • 5.1.0-3
    • 5.1.2-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • aiosmtplib Ubuntu:26.04:LTS

    Versions
    • 4.0.0-1
    • 4.0.2-1
    • 5.0.0-1
    • 5.1.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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