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.
Project Subscriptions
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Advisories
| Source | ID | Title |
|---|---|---|
Github GHSA |
GHSA-v3q9-hj7j-63hq | aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Tue, 18 Aug 2026 18:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | aiosmtplib: SMTP command injection via CR/LF in sender/recipient address | |
| Weaknesses | CWE-77 CWE-93 |
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| References |
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| Metrics |
cvssV4_0
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Projects
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-08-18T17:54:23.124Z
Reserved: 2026-06-09T17:30:33.457Z
Link: CVE-2026-53533
No data.
Status : Received
Published: 2026-08-18T18:18:20.513
Modified: 2026-08-18T18:18:20.513
Link: CVE-2026-53533
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OpenCVE Enrichment
No data.
Github GHSA