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Vulnerability Note VU#686862MIT Kerberos 5 krb5_aname_to_localname() contains several heap overflowsOverviewMIT Kerberos 5 contains several heap buffer overflow vulnerabilities in code that translates Kerberos principal names to local UNIX account names. An authenticated, remote attacker could execute arbitrary code on a vulnerable system with root privileges.I. DescriptionMIT Kerberos 5 contains several heap buffer overflow vulnerabilities in a library that translates Kerberos principal names to local UNIX account names. From MIT krb5 Security Advisory 2004-001:krb5_aname_to_localname() translates a Kerberos principal name to a local account name, typically a UNIX username. In the file src/lib/krb5/os/an_to_ln.c, the helper functions aname_replacer(), do_replacement(), and rule_an_to_ln() do not perform adequate checks of the lengths of strings which contain the name of the principal whose authorization is being checked.
Only kerberos enabled services that enable explicit or rules-based krb5_aname_to_localname() mapping are vulnerable. In the case of the explicit mapping vulnerability, the attacker would need to authenticate using a principal name that is present in the explicit mapping list. In the case of the rules-based mapping vulnerabilities, the attacker would need the ability to create specially crafted principal names in the local realm or in a realm accessible via cross-realm authentication. II. ImpactAn authenticated, remote attacker could execute arbitrary code on a system using krb5_aname_to_localname() mapping. The vulnerable library is loaded by services that use Kerberos authentication (e.g., telnetd, klogind), and in most cases these services run with root privileges.III. SolutionApply a patch or upgrade
References
This vulnerability was reported by the MIT Kerberos Development Team. This document was written by Art Manion.
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