The receive_msg function in receive.c in the SMTP daemon in Exim 4.88 and 4.89 allows remote attackers to execute arbitrary code or cause a denial of service (use-after-free) via vectors involving BDAT commands.
openwall.com/lists/oss-security/2017/11/25/1
openwall.com/lists/oss-security/2017/11/25/2
openwall.com/lists/oss-security/2017/11/25/3
www.openwall.com/lists/oss-security/2021/05/04/7
www.securitytracker.com/id/1039872
bugs.exim.org/show_bug.cgi?id=2199
git.exim.org/exim.git/commit/4090d62a4b25782129cc1643596dc2f6e8f63bde
git.exim.org/exim.git/commitdiff/4e6ae6235c68de243b1c2419027472d7659aa2b4
github.com/LetUsFsck/PoC-Exploit-Mirror/tree/master/CVE-2017-16944
lists.exim.org/lurker/message/20171125.034842.d1d75cac.en.html
www.debian.org/security/2017/dsa-4053