CVE-2026-53533 json
aiosmtplib: SMTP command injection via CR/LF in sender/recipient address
published 2026-07-07 4 mo ago modified 2026-10-22 17 d ago also GHSA-v3q9-hj7j-63hq , PYSEC-2026-2338 , EUVD-2026-61138
- cvss
- 6.9
- version 4.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 44%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- pypi aiosmtplib 5.1.1
- aiosmtplib Debian 14 5.1.2-1
debian advisories DEBIAN-CVE-2026-53533
- python-aiosmtplib openSUSE Tumbleweed 5.1.1-1.1
opensuse advisories openSUSE-SU-2026:11035-1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 2 mo ago
Exploit prediction
0.53% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 6.9 | 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 |
| CNA | 4.0 | 6.9 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | aiosmtplib | <5.1.1 |
5.1.1 |
Affected products
- cole aiosmtplib
Classification
References
- github.com /cole/aiosmtplib/commit/8eaf6efc9a8f59e2e09d3ef11246a058c46bd3ba
-
github.com
/cole/aiosmtplib/security/advisories/GHSA-v3q9-hj7j-63hq
web
- github.com /cole/aiosmtplib/releases/tag/v5.1.1
-
github.com
/cole/aiosmtplib
package
-
pypi.org
/project/aiosmtplib
package
-
github.com
/advisories/GHSA-v3q9-hj7j-63hq
advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-53533
advisory
Sources
- CVE List CVE-2026-53533
- GitHub Advisory GHSA-v3q9-hj7j-63hq
- NVD CVE-2026-53533
- OSV PYSEC-2026-2338
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.