https://gitlab.freedesktop.org/slirp/libslirp/-/commit/3e6e68e779c9051590250a87214dabf91e70949a

Index: src/slirp.c
--- src/slirp.c.orig
+++ src/slirp.c
@@ -1581,9 +1581,12 @@ static bool check_guestfwd(Slirp *slirp, struct in_add
                              (htonl(0x0204) & ~slirp->vnetwork_mask.s_addr);
     }
     if ((guest_addr->s_addr & slirp->vnetwork_mask.s_addr) !=
-            slirp->vnetwork_addr.s_addr ||
-        guest_addr->s_addr == slirp->vhost_addr.s_addr ||
-        guest_addr->s_addr == slirp->vnameserver_addr.s_addr) {
+            slirp->vnetwork_addr.s_addr) {
+        return false;
+    }
+    if (!slirp->disable_dns &&
+        guest_addr->s_addr == slirp->vnameserver_addr.s_addr &&
+        guest_port == 53) {
         return false;
     }
 
