An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1. By sending a handcrafted message, a buffer overflow may happen. This can be used to execute code remotely.
https://exim.org/static/doc/security/CVE-2018-6789.txt
http://www.openwall.com/lists/oss-security/2018/02/07/2
https://www.debian.org/security/2018/dsa-4110
https://lists.debian.org/debian-lts-announce/2018/02/msg00009.html
https://git.exim.org/exim.git/commit/cf3cd306062a08969c41a1cdd32c6855f1abecf1
http://openwall.com/lists/oss-security/2018/02/10/2
http://www.securityfocus.com/bid/103049
https://devco.re/blog/2018/03/06/exim-off-by-one-RCE-exploiting-CVE-2018-6789-en/
http://www.securitytracker.com/id/1040461
https://usn.ubuntu.com/3565-1/
https://www.exploit-db.com/exploits/44571/
https://www.exploit-db.com/exploits/45671/
http://packetstormsecurity.com/files/162959/Exim-base64d-Buffer-Overflow.html
Source: MITRE
Published: 2018-02-08
Updated: 2021-06-03
Type: CWE-119
Base Score: 7.5
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P
Impact Score: 6.4
Exploitability Score: 10
Severity: HIGH
Base Score: 9.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 3.9
Severity: CRITICAL