CVE-2024-39929Network attack vector

Executable-attachment delivery via split filename parameters

Published Jul 4, 2024 · Updated Mar 18, 2025

Security-filter bypass in Exim 4.97.1 and earlier allows remote attackers to deliver blocked executable attachments via crafted email. The MIME parser fails to assemble a filename split across multiple RFC 2231 parameters before exposing $mime_filename to extension checks. Exploitation requires $mime_filename-based blocking; the bypass only places an attachment in a mailbox, and execution requires recipient interaction.

CVSS severity7.6
High
EPSS probability41.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Security-filter bypass in Exim 4.97.1 and earlier allows remote attackers to deliver blocked executable attachments via crafted email. The MIME parser fails to assemble a filename split across multiple RFC 2231 parameters before exposing $mime_filename to extension checks. Exploitation requires $mime_filename-based blocking; the bypass only places an attachment in a mailbox, and execution requires recipient interaction.

The record

CVE
CVE-2024-39929
Published
Jul 4, 2024
Updated
Mar 18, 2025
Vendor
LibSPF2 Project
Product
Exim
Classifications
CWE-116, T1566.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 4, 2024CVE publishedPublication date reported by the CVE source.
  2. Mar 18, 2025Record 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 <=4.97.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

LibSPF2 Project · Eximversion=0 <=4.97.1

Published CVSS scores

7.6Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
T1566.001Spearphishing Attachment

Public exploit references

No public exploit references are available in this record.

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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