The asn1_decode_generaltime function in lib/krb5/asn.1/asn1_decode.c in the ASN.1 GeneralizedTime decoder in MIT Kerberos 5 (aka krb5) before 1.6.4 allows remote attackers to cause a denial of service (daemon crash) or possibly execute arbitrary code via vectors involving an invalid DER encoding that triggers a free of an uninitialized pointer.
http://www.vmware.com/security/advisories/VMSA-2009-0008.html
http://www.us-cert.gov/cas/techalerts/TA09-133A.html
http://www.ubuntu.com/usn/usn-755-1
http://support.avaya.com/elmodocs2/security/ASA-2009-142.htm
http://support.apple.com/kb/HT3549
http://security.gentoo.org/glsa/glsa-200904-09.xml
http://rhn.redhat.com/errata/RHSA-2009-0410.html
http://rhn.redhat.com/errata/RHSA-2009-0409.html