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.
Version 4 of the Kerberos protocol (krb4), as used in Heimdal and other packages, allows an attacker to impersonate any principal in a realm via a chosen-plaintext attack.
The kadm_ser_in function in (1) the Kerberos v4compatibility administration daemon (kadmind4) in the MIT Kerberos 5 (krb5) krb5-1.2.6 and earlier, (2) kadmind in KTH Kerberos 4 (eBones) before 1.2.1, and (3) kadmind in KTH Kerberos 5 (Heimdal) before 0.5.1 when compiled with Kerberos 4 support, does not properly verify the length field of a request, which allows remote attackers to execute arbitrary code via a buffer overflow attack.
Unknown vulnerabilities in Heimdal before 0.5 with unknown impact, possibly in the (1) kadmind and (2) kdc servers, may allow remote or local attackers to gain root or other access, but not via buffer overflows (CVE-2002-1225).