{"cve":"CVE-2026-53533","nvd":{"published":"2026-08-18T18:18:20.513","modified":"2026-10-22T22:10:00.250","status":"Deferred","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.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:H/SA:N","score":6.9},"cvss_v3":null,"cwes":["CWE-77","CWE-93"],"references":["https://github.com/cole/aiosmtplib/commit/8eaf6efc9a8f59e2e09d3ef11246a058c46bd3ba","https://github.com/cole/aiosmtplib/releases/tag/v5.1.1","https://github.com/cole/aiosmtplib/security/advisories/GHSA-v3q9-hj7j-63hq"],"products":[],"source":"nvd","synced_at":"2026-10-23T16:39:26.291718493+00:00"},"epss":{"cve":"CVE-2026-53533","score":0.00525,"percentile":0.44243,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-v3q9-hj7j-63hq","url":"https://osv.dev/vulnerability/GHSA-v3q9-hj7j-63hq","summary":"aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address","modified":"2026-09-10T03:50:53.029848773Z","packages":[{"ecosystem":"PyPI","name":"aiosmtplib","purl":"pkg:pypi/aiosmtplib","ranges":["<5.1.1"],"fixed":["5.1.1"]}]},{"id":"PYSEC-2026-2338","url":"https://osv.dev/vulnerability/PYSEC-2026-2338","summary":"aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address","modified":"2026-07-13T16:31:35.503143756Z","packages":[{"ecosystem":"PyPI","name":"aiosmtplib","purl":"pkg:pypi/aiosmtplib","ranges":["<5.1.1"],"fixed":["5.1.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}