OpenBSD kernel 3.3 and 3.4 allows local users to cause a denial of service (kernel panic) and possibly execute arbitrary code in 3.4 via a program with an invalid header that is not properly handled by (1) ibcs2_exec.c in the iBCS2 emulation (compat_ibcs2) or (2) exec_elf.c, which leads to a stack-based buffer overflow.