arch/x86/kernel/ptrace.c in the Linux kernel before 2.6.25.10 on the x86_64 platform leaks task_struct references into the sys32_ptrace function, which allows local users to cause a denial of service (system crash) or have unspecified other impact via unknown vectors, possibly a use-after-free vulnerability.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2008-3077)