Software Engineering Institute

A vulnerability exists in the way the principal renaming operation used by the Kerberos administration daemon handles strings and a fixed-size stack buffer. This vulnerability may cause a buffer overflow vulnerability that could allow a remote, authenticated user to execute arbitrary code. According to MIT krb5 Security Advisory MITKRB5-SA-2007-005:

The kadmind code which performs the principal renaming operation passes unchecked string arguments to a sprintf() call which has a fixed-size stack buffer as its destination. These strings are the old and new principal names passed to the rename operation. The attacker needs to authenticate to kadmind to perform this attack, but no administrative privileges are required because the vulnerable code executes prior to privilege verification.
Note that this issue affects all releases of MIT krb5 up to and including krb5-1.6.1. MIT has been provided with proof-of-concept exploit code, but it's not clear whether the exploit code is publicly available yet.

A remote, authenticated user may be able to execute arbitrary code on an affected system or cause the affected program to crash, resulting in a denial of service. Secondary impacts of code execution include complete compromise of the Kerberos key database.

Apply a patch
A patch can be obtained from MIT krb5 Security Advisory MITKRB5-SA-2007-005. MIT also states that this will be addressed in the upcoming krb5-1.6.2 and krb5-1.5.4 releases.