The Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.7 does not properly restrict the use of TGT credentials for armoring TGS requests, which might allow remote authenticated users to impersonate a client by rewriting an inner request, aka a "KrbFastReq forgery issue."
http://www.vupen.com/english/advisories/2010/3118
http://www.vupen.com/english/advisories/2010/3094
http://www.vmware.com/security/advisories/VMSA-2011-0007.html
http://www.ubuntu.com/usn/USN-1030-1
http://www.securitytracker.com/id?1024803
http://www.securityfocus.com/bid/45122
http://www.securityfocus.com/archive/1/517739/100/0/threaded
http://www.securityfocus.com/archive/1/514953/100/0/threaded
http://www.mandriva.com/security/advisories?name=MDVSA-2010:246
http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2010-007.txt
http://support.apple.com/kb/HT4581
http://lists.vmware.com/pipermail/security-announce/2011/000133.html
http://lists.opensuse.org/opensuse-security-announce/2010-12/msg00006.html
http://lists.opensuse.org/opensuse-security-announce/2010-12/msg00000.html
http://lists.apple.com/archives/security-announce/2011/Mar/msg00006.html