diff --git a/server/reds.c b/server/reds.c
index f40b65c1..86a33d53 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -2202,7 +2202,8 @@ static void reds_handle_read_header_done(void *opaque)
 
     reds->peer_minor_version = header->minor_version;
 
-    if (header->size < sizeof(SpiceLinkMess)) {
+    /* the check for 4096 is to avoid clients to cause arbitrary big memory allocations */
+    if (header->size < sizeof(SpiceLinkMess) || header->size > 4096) {
         reds_send_link_error(link, SPICE_LINK_ERR_INVALID_DATA);
         spice_warning("bad size %u", header->size);
         reds_link_free(link);