The receive_msg function in receive.c in the SMTP daemon in Exim 4.88 and 4.89 allows remote attackers to cause a denial of service (infinite loop and stack exhaustion) via vectors involving BDAT commands and an improper check for a '.' character signifying the end of the content, related to the bdat_getc function.
Exim supports the use of multiple "-p" command line arguments which are malloc()'ed and never free()'ed, used in conjunction with other issues allows attackers to cause arbitrary code execution. This affects exim version 4.89 and earlier. Please note that at this time upstream has released a patch (commit 65e061b76867a9ea7aeeb535341b790b90ae6c21), but it is not known if a new point release is available that addresses this issue at this time.