diff --git a/sys/net/if_gif.c b/sys/net/if_gif.c
--- a/sys/net/if_gif.c
+++ b/sys/net/if_gif.c
@@ -405,6 +405,21 @@
 {
 	uint32_t af;
 
+	/*
+	 * Normally, when a gif(4) interface is a member of bridge(4), bridge_enqueue()
+	 * only calls gif_transmit(), so this code path should never be reached.
+	 * However, if the outer protocol of the gif tunnel is IPv6, certain special
+	 * IPv6 multicast control messages, such as MLDv2, destinated for ff02::/16
+	 * may still reach gif_output() due to internal behavior of IPv6 stack.
+	 *
+	 * Therefore, the kernel should not panic because of such packets; instead,
+	 * they should be silently dropped.
+	 */
+	if (ifp->if_bridge != NULL && dst->sa_family == AF_INET6) {
+		m_freem(m);
+		return (0);
+	}
+
 	KASSERT(ifp->if_bridge == NULL,
 	    ("%s: unexpectedly called with bridge attached", __func__));