Debian Linux Security Advisory 4944-1 - It was discovered that the Key Distribution Center (KDC) in krb5, the MIT implementation of Kerberos, is prone to a NULL pointer dereference flaw. An unauthenticated attacker can take advantage of this flaw to cause a denial of service (KDC crash) by sending a request containing a PA-ENCRYPTED-CHALLENGE padata element without using FAST.
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