untrusted comment: signature from openbsd 6.0 base secret key
RWSho3oKSqgLQ8YVCKjPokLrn99Y/6LRUX0kW5slAa2hDjh9otci/Z3FRDdpTKReGSU/HuUXS7ARXvA7juDoIEAKQe5fNmYk+Ao=

OpenBSD 6.0 errata 20, Mar 20, 2017

ELF auxiliary vector storage leaks piece of kernel stack.

Apply by doing:
    signify -Vep /etc/signify/openbsd-60-base.pub -x 020_exec_elf.patch.sig \
        -m - | (cd /usr/src && patch -p0)

And then rebuild and install a new kernel:
    cd /usr/src/sys/arch/`machine`/conf
    KK=`sysctl -n kern.osversion | cut -d# -f1`
    config $KK
    cd ../compile/$KK
    make
    make install

Index: sys/kern/exec_elf.c
===================================================================
RCS file: /cvs/src/sys/kern/exec_elf.c,v
retrieving revision 1.139
retrieving revision 1.140
diff -u -p -r1.139 -r1.140
--- sys/kern/exec_elf.c	5 Mar 2017 00:45:30 -0000	1.139
+++ sys/kern/exec_elf.c	20 Mar 2017 00:05:21 -0000	1.140
@@ -802,6 +802,7 @@ exec_elf_fixup(struct proc *p, struct ex
 	 * linked binaries
 	 */
 	if (error == 0) {
+		memset(&ai, 0, sizeof ai);
 		a = ai;
 
 		a->au_id = AUX_phdr;