Comment 0 for bug 2064350

The file is missing from libpam-modules.
This breaks, for example, existing vsftp configs if it is configured to use pam_userdb.so

Log:

vsftpd: PAM unable to dlopen(pam_userdb.so): /usr/lib/security/pam_userdb.so: cannot open shared object file: No such file or directory
vsftpd: PAM adding faulty module: pam_userdb.so

Apparently there was a change which removed this in the past, and it might be the removal has not been undone, while the package has been released nevertheless.

http://changelogs.ubuntu.com/changelogs/pool/main/p/pam/pam_1.5.3-5ubuntu5/changelog

  * For now remove libdb-dev so that libdb-dev can undergo time_t
    transition. That means this version of pam does not include
    pam_userdb, which makes pam unsuitable for release.