Heimdal 0.6.x before 0.6.1 and 0.5.x before 0.5.3 does not properly perform certain consistency checks for cross-realm requests, which allows remote attackers with control of a realm to impersonate others in the cross-realm trust path.
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-04:08.heimdal.asc
ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.5/common/009_kerberos.patch
security.gentoo.org/glsa/glsa-200404-09.xml
www.debian.org/security/2004/dsa-476
www.pdc.kth.se/heimdal/advisory/2004-04-01/
exchange.xforce.ibmcloud.com/vulnerabilities/15701