MIT krb5 is the free implementation of the Kerberos network authentication protocol by the Massachusetts Institute of Technology.
The MIT Kerberos 5 administration library libkadm5srv contains a heap overflow in the code handling password changing.
Under specific circumstances an attacker could execute arbitary 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 mit-krb5 users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=app-crypt/mit-krb5-1.3.6"