krb5: kadmind invalid pointer free() (MITKRB5-SA-004)

The processchpwrequest function in schpw.c in the password-changing functionality in kadmind in MIT Kerberos 5 aka krb5 1.7 through 1.9 frees an invalid pointer, which allows remote attackers to execute arbitrary code or cause a denial of service daemon crash via a crafted request that triggers a...