Arbitrary Command Injection Affecting aiosmtplib package, versions <5.1.2-1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-DEBIAN14-AIOSMTPLIB-19166092
- published22 Aug 2026
- disclosed18 Aug 2026
Introduced: 18 Aug 2026
NewCVE-2026-53533 (opens in a new tab)How to fix?
Upgrade Debian:14 aiosmtplib to version 5.1.2-1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream aiosmtplib package and not the aiosmtplib package as distributed by Debian.
See How to fix? for Debian:14 relevant fixed versions and status.
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.