authpam.c in courier-authdaemon for Courier Mail Server 0.37.3 through 0.52.1, when using pam_tally, does not call the pam_acct_mgmt function to verify that access should be granted, which allows attackers to authenticate to the server using accounts that have been disabled.

spf.c in Courier Mail Server does not properly handle DNS failures when looking up Sender Policy Framework (SPF) records, which could allow attackers to cause memory corruption.