CVE-2024-27305: aiosmtpd is a reimplementation of the Python stdlib smtpd.py based on asyncio

Q: How do I fix CVE-2024-27305?

aiosmtpd: upgrade to 1.4.5. Exact commands for each OS are on this page.

Q: Is CVE-2024-27305 being exploited?

CVE-2024-27305 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2024-27305 affect?

CVE-2024-27305 affects aiosmtpd. Severity is medium (CVSS 5.3). 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.

Q: How urgent is CVE-2024-27305?

Priority 31/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2024-27305 is a medium-severity flaw (CVSS 5.3) affecting aiosmtpd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 69%)
CISA exploited list	No
Weakness	CWE-345
Published	2024-03-12
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: aio-libs

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2024-03-12 21:15 UTCPublished CVE record published
2026-06-17 07:19 UTCUpdated Record last modified

aio-libs aiosmtpd UPGRADE

Affected: < 1.4.5

Fixed in: 1.4.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy aiosmtpd || rpm -q aiosmtpd || aiosmtpd --version

2. UPGRADE to 1.4.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade aiosmtpd

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade aiosmtpd

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2024-27305?

aiosmtpd: upgrade to 1.4.5. Exact commands for each OS are on this page.

Is CVE-2024-27305 being exploited?

CVE-2024-27305 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2024-27305 affect?

CVE-2024-27305 affects aiosmtpd. Severity is medium (CVSS 5.3). 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.

How urgent is CVE-2024-27305?

Priority 31/100. Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities · Postfix vulnerabilities

References

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