backport #7486

Author: d-a-v

libraries/ESP8266WiFi/src/ESP8266WiFiGeneric.cpp

@@ -233,6 +233,16 @@ void ESP8266WiFiGenericClass::_eventCallback(void* arg)
         WiFiClient::stopAll();
     }
 
+    if (event->event == EVENT_STAMODE_AUTHMODE_CHANGE) {
+        auto& src = event->event_info.auth_change;
+        if ((src.old_mode != AUTH_OPEN) && (src.new_mode == AUTH_OPEN)) {
+            // CVE-2020-12638 workaround.  When we get a change to AUTH_OPEN from any other mode, drop the WiFi link because it's a downgrade attack
+            // TODO - When upgrading to 3.x.x with fix, remove this code
+            DEBUG_WIFI("WIFI_EVENT_STAMODE_AUTHMODE_CHANGE from encrypted(%d) to AUTH_OPEN, potential downgrade attack. Reconnecting WiFi. See CVE-2020-12638 for more details\n", src.old_mode);
+            WiFi.reconnect();  // Disconnects from STA and then reconnects
+        }
+    }
+
     for(auto it = std::begin(sCbEventList); it != std::end(sCbEventList); ) {
         WiFiEventHandler &handler = *it;
         if (handler->canExpire() && handler.unique()) {