Answer in brief
CVE-2026-53533 records a Medium severity vulnerability in aiosmtplib: SMTP command injection via CR/LF in sender/recipient address. The current sources do not mark it as known exploited. The current feed maps cole/aiosmtplib (generic), aiosmtplib (pip). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps cole/aiosmtplib (generic), aiosmtplib (pip). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| cole/aiosmtplibgeneric | < 5.1.1 | Not reported |
| aiosmtplibpip | <=5.1.0 | 5.1.1 |
Published upstream
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 8, 2026
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.
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2026-53533 records a Medium severity vulnerability in aiosmtplib: SMTP command injection via CR/LF in sender/recipient address. The current sources do not mark it as known exploited. The current feed maps cole/aiosmtplib (generic), aiosmtplib (pip). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps cole/aiosmtplib (generic), aiosmtplib (pip). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| cole/aiosmtplibgeneric | < 5.1.1 | Not reported |
| aiosmtplibpip | <=5.1.0 | 5.1.1 |
Published upstream
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 18, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 8, 2026
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.
Quoted source text, attributed separately from HOL analysis.