aiosmtpd vulnerable to SMTP smuggling

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2024-27305: 0.37% estimated exploitation activity in the next 30 days; percentile 31.43 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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 also existed in other SMTP software like Postfix (https://www.postfix.org/smtp-smuggling.html). Details Detailed information on SMTP smuggling can be found in the full blog post (https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/) or on the Postfix homepage (https://www.postfix.org/smtp-smuggling.html). (and soon on the official website https://smtpsmuggling.com/) Impact With the right SMTP server constellation, an attacker can send spoofed e-mails to inbound/receiving aiosmtpd instances.

Published by the source

13 Mar 2024, 15:33 UTC

Last modified by the source

10 Jun 2026, 17:14 UTC

Source last checked

26 Oct 2026, 13:30 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-pr2m-px7j-xg65

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-pr2m-px7j-xg65

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# Patch Next advisory brief: CVE-2024-27305

Advisory: aiosmtpd vulnerable to SMTP smuggling
IDs: CVE-2024-27305, GHSA-pr2m-px7j-xg65
Record: https://patchnext.com/advisories/cve-2024-27305 (revision 2, source checked 26 Oct 2026, 13:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: aiosmtpd 1.4.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI aiosmtpd: affected < 1.4.5; fixed in 1.4.5

## Suggested inspection (read-only)
- `python -m pip show aiosmtpd`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on aiosmtpd.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-pr2m-px7j-xg65 (OSV record GHSA-pr2m-px7j-xg65 lists affected ranges: PyPI aiosmtpd >=0 <1.4.5 (fixed))
- Verified: https://github.com/advisories/GHSA-pr2m-px7j-xg65 (GitHub-reviewed advisory GHSA-pr2m-px7j-xg65 lists affected ranges: PyPI aiosmtpd >=0 <1.4.5)

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