untrusted comment: signature from openbsd 5.9 base secret key
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OpenBSD 5.9 errata 26, Sep 17, 2016:

Limit the number of wscons fonts that can be loaded into the kernel.

Apply by doing:
   signify -Vep /etc/signify/openbsd-59-base.pub -x 026_wsfont.patch.sig \
       -m - | (cd /usr/src && patch -p0)

And then rebuild and install a 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/dev/wscons/wsconsio.h
===================================================================
RCS file: /cvs/src/sys/dev/wscons/wsconsio.h,v
retrieving revision 1.73
retrieving revision 1.73.2.1
diff -u -p -r1.73 -r1.73.2.1
--- sys/dev/wscons/wsconsio.h   12 Dec 2015 12:30:18 -0000      1.73
+++ sys/dev/wscons/wsconsio.h   16 Sep 2016 15:01:05 -0000      1.73.2.1
@@ -404,6 +404,7 @@ struct wsdisplay_cursor {
struct wsdisplay_font {
       char name[WSFONT_NAME_SIZE];
       int index;
+#define WSDISPLAY_MAXFONTCOUNT 8
       int firstchar, numchars;
       int encoding;
#define WSDISPLAY_FONTENC_ISO 0
Index: sys/dev/wsfont/wsfont.c
===================================================================
RCS file: /cvs/src/sys/dev/wsfont/wsfont.c,v
retrieving revision 1.42
retrieving revision 1.42.2.1
diff -u -p -r1.42 -r1.42.2.1
--- sys/dev/wsfont/wsfont.c     13 Sep 2015 16:44:30 -0000      1.42
+++ sys/dev/wsfont/wsfont.c     16 Sep 2016 15:01:05 -0000      1.42.2.1
@@ -450,13 +450,21 @@ wsfont_add(struct wsdisplay_font *font,
{
       static int cookiegen = 666;
       struct font *ent;
-       int s;
+       int s, fontc = 0;

       s = splhigh();

       /* Don't allow exact duplicates */
       if (wsfont_find(font->name, font->fontwidth, font->fontheight,
           font->stride) >= 0) {
+               splx(s);
+               return (-1);
+       }
+
+       TAILQ_FOREACH(ent, &fontlist, chain)
+               fontc++;
+
+       if (fontc >= WSDISPLAY_MAXFONTCOUNT) {
               splx(s);
               return (-1);
       }