CVE-2024-39929 — Exim through 4
Exim through 4.97.1 misparses a multiline RFC 2231 header filename, and thus remote attackers can bypass a $mime_filename extension-blocking protection mechanism, and potentially deliver executable attachments to the mailboxes of end users.
Published
2024-07-04T00:00:00.000Z
Last modified
2025-03-18T15:37:58.804Z
01What is this vulnerability?
Exim through 4.97.1 misparses a multiline RFC 2231 header filename, and thus remote attackers can bypass a $mime_filename extension-blocking protection mechanism, and potentially deliver executable attachments to the mailboxes of end users.
02Affected products
| Vendor | Product | Versions |
|---|
| n | a / n/a | n/a |
03Active exploitation status
Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.
04Recommended remediation
- Patch to a fixed version listed in the vendor advisory (see references below).
- Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
- Hunt historical logs for exploitation indicators — see Detection signatures below.
05Technical details
For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.
06Detection signatures
Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:
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07Related CVEs
No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.
08Timeline
- Published: 2024-07-04T00:00:00.000Z
- Last modified: 2025-03-18T15:37:58.804Z
09References
- git.exim.org — https://git.exim.org/exim.git/commit/6ce5c70cff8989418e05d01fd2a57703007a6357
- git.exim.org — https://git.exim.org/exim.git/commit/1b3209b0577a9327ebb076f3b32b8a159c253f7b
- github.com — https://github.com/Exim/exim/compare/exim-4.98-RC2...exim-4.98-RC3
- www.rfc-editor.org — https://www.rfc-editor.org/rfc/rfc2231.txt
- bugs.exim.org — https://bugs.exim.org/show_bug.cgi?id=3099#c4
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