CVE-2024-27305Public exploitNetwork attack vector

Sender spoofing via bare-LF message parsing

Published Mar 12, 2024 · Updated Aug 2, 2024

SMTP smuggling in aio-libs aiosmtpd before 1.4.5 allows remote attackers to spoof sender addresses through crafted message data. The smtp_DATA parser treated a bare line feed as a line ending, so an LF-dot-CRLF sequence could be interpreted differently by another SMTP server and aiosmtpd. Exploitation requires a mismatched SMTP server constellation and can deliver a spoofed message with an attacker-chosen envelope sender.

CVSS severity5.3
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SMTP smuggling in aio-libs aiosmtpd before 1.4.5 allows remote attackers to spoof sender addresses through crafted message data. The smtp_DATA parser treated a bare line feed as a line ending, so an LF-dot-CRLF sequence could be interpreted differently by another SMTP server and aiosmtpd. Exploitation requires a mismatched SMTP server constellation and can deliver a spoofed message with an attacker-chosen envelope sender.

The record

CVE
CVE-2024-27305
Published
Mar 12, 2024
Updated
Aug 2, 2024
Vendor
aio-libs
Product
aiosmtpd
Classifications
CWE-345, T1566
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.4.5
  2. Affected versionversion=< 1.4.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

aio-libs · aiosmtpdversion=0 <1.4.5; version=< 1.4.5

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-345Insufficient Verification of Data Authenticity
T1566Phishing

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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