untrusted comment: signature from openbsd 5.7 base secret key
RWSvUZXnw9gUbzlqxwSdqP/pZmYC8V1nvdAZ9A5dNmHGczeQrT493IMx1ndKCIVOzolPKwXR5Ahft4HOAFg2WDxSTw8XSpjJggo=

OpenBSD 5.7 errata 20, Nov 9, 2015

Insufficient validation of RSN element group cipher values in 802.11
beacons and probe responses could result in system panics.

Apply by doing:
   signify -Vep /etc/signify/openbsd-57-base.pub -x 020_rsn.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/net80211/ieee80211_input.c
===================================================================
RCS file: /cvs/src/sys/net80211/ieee80211_input.c,v
retrieving revision 1.132
diff -u -p -r1.132 ieee80211_input.c
--- sys/net80211/ieee80211_input.c      9 Feb 2015 03:09:57 -0000       1.132
+++ sys/net80211/ieee80211_input.c      8 Nov 2015 12:04:42 -0000
@@ -1232,7 +1232,9 @@ ieee80211_parse_rsn_body(struct ieee8021
       if (frm + 4 > efrm)
               return 0;
       rsn->rsn_groupcipher = ieee80211_parse_rsn_cipher(frm);
-       if (rsn->rsn_groupcipher == IEEE80211_CIPHER_USEGROUP)
+       if (rsn->rsn_groupcipher == IEEE80211_CIPHER_NONE ||
+           rsn->rsn_groupcipher == IEEE80211_CIPHER_USEGROUP ||
+           rsn->rsn_groupcipher == IEEE80211_CIPHER_BIP)
               return IEEE80211_STATUS_BAD_GROUP_CIPHER;
       frm += 4;

@@ -1296,6 +1298,8 @@ ieee80211_parse_rsn_body(struct ieee8021
       if (frm + 4 > efrm)
               return 0;
       rsn->rsn_groupmgmtcipher = ieee80211_parse_rsn_cipher(frm);
+       if (rsn->rsn_groupmgmtcipher != IEEE80211_CIPHER_BIP)
+               return IEEE80211_STATUS_BAD_GROUP_CIPHER;

       return IEEE80211_STATUS_SUCCESS;
}