mit-krb5 is the free implementation of the Kerberos network authentication protocol by the Massachusetts Institute of Technology.
The library function krb5_aname_to_localname() contains multiple buffer overflows. This is only exploitable if explicit mapping or rules-based mapping is enabled. These are not enabled as default.
With explicit mapping enabled, an attacker must authenticate using a principal name listed in the explicit mapping list.
With rules-based mapping enabled, an attacker must first be able to create arbitrary principal names either in the local realm Kerberos realm or in a remote realm from which the local realm's service are reachable by cross-realm authentication.
An attacker could use these vulnerabilities to execute arbitrary code with the permissions of the user running mit-krb5, which could be the root user.
There is no known workaround at this time. All users are encouraged to upgrade to the latest available version.
mit-krb5 users should upgrade to the latest version:
# emerge sync
# emerge -pv ">=app-crypt/mit-krb5-1.3.3-r1"
# emerge ">=app-crypt/mit-krb5-1.3.3-r1"