An issue in provider/libserver/ECKrbAuth.cpp of Kopano Core <= v11.0.2.51 contains an issue which allows attackers to authenticate even if the user account or password is expired. It also exists in the predecessor Zarafa Collaboration Platform (ZCP) in provider/libserver/ECPamAuth.cpp of Zarafa >= 6.30 (introduced between 6.30.0 RC1e and 6.30.8 final).