The do_coredump function in fs/exec.c in the Linux kernel 2.6.19 sets the flag variable to O_EXCL but does not use it, which allows context-dependent attackers to modify arbitrary files via a rewrite attack during a core dump.
http://secunia.com/advisories/23349
http://support.avaya.com/css/P8/documents/100073666
http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.19.1
http://www.securityfocus.com/bid/21591
http://www.trustix.org/errata/2006/0074/
http://www.vupen.com/english/advisories/2006/5002
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10797
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A7446