hfaxd in HylaFAX before 4.2.1, when installed with a "weak" hosts.hfaxd file, allows remote attackers to authenticate and bypass intended access restrictions via a crafted (1) username or (2) hostname that satisfies a regular expression that is matched against a hosts.hfaxd entry without a password.
http://www.mandriva.com/security/advisories?name=MDKSA-2005:006
http://www.debian.org/security/2004/dsa-634
http://security.gentoo.org/glsa/glsa-200501-21.xml
http://secunia.com/advisories/13812