#VU94107 Input validation error in Exim - CVE-2024-39929

Vulnerability identifier: #VU94107

Vulnerability risk: Medium

CVSSv4.0: 5.5 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/U:Green]

CVE-ID: CVE-2024-39929

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Exim
Server applications / Mail servers

Vendor: Exim

Description

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to insufficient validation of RFC 2231 header filename. A remote attacker can bypass a $mime_filename extension-blocking protection mechanism and deliver malicious executable files to the mailboxes.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Exim: 4.00 - 4.97.1

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External links
https://git.exim.org/exim.git/commit/6ce5c70cff8989418e05d01fd2a57703007a6357
https://git.exim.org/exim.git/commit/1b3209b0577a9327ebb076f3b32b8a159c253f7b
https://github.com/Exim/exim/compare/exim-4.98-RC2...exim-4.98-RC3
https://www.rfc-editor.org/rfc/rfc2231.txt
https://bugs.exim.org/show_bug.cgi?id=3099#c4

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.