untrusted comment: signature from openbsd 5.9 base secret key
RWQJVNompF3pwQK9rovw7QRGOnvldZVEX7OHumsMhH+r1pVAFO2a9YSTgx0zY3x6+ixhQTLFtbWHxdM+1ku/AZCzDYQJU24FAgk=

OpenBSD 5.9 errata 37, Mar 20, 2017

ELF auxiliary vector storage leaks piece of kernel stack.

Apply by doing:
    signify -Vep /etc/signify/openbsd-59-base.pub -x 037_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 1.119
diff -u -p -r1.119 exec_elf.c
--- sys/kern/exec_elf.c	2 Nov 2015 16:31:55 -0000	1.119
+++ sys/kern/exec_elf.c	20 Mar 2017 03:03:18 -0000
@@ -816,6 +816,7 @@ ELFNAME2(exec,fixup)(struct proc *p, str
 	 * linked binaries
 	 */
 	if (error == 0) {
+		memset(&ai, 0, sizeof ai);
 		a = ai;
 
 		a->au_id = AUX_phdr;