This is a bugfix and security release. Users of mosquitto 1.4 are strongly advised to upgrade. Upgrading from earlier versions is recommended but not as important.


  • Fix possible crash under heavy network load. Closes #463241. This bug only affects version 1.4.
  • Fix possible crash when using pattern ACLs.
  • Fix problems parsing config strings with multiple leading spaces. Closes #462154.
  • Websockets clients are now periodically disconnected if they have not maintained their keepalive timer. Closes #461619.
  • Fix possible minor memory leak on acl parsing.

Client library

  • Inflight limits should only apply to outgoing messages. Closes #461620.
  • Fix reconnect bug on Windows. Closes #463000.
  • Return -1 on error from mosquitto_socket(). Closes #461705.
  • Fix crash on multiple calls to mosquitto_lib_init/mosquitto_lib_cleanup. Closes #462780.
  • Allow longer paths on Windows. Closes #462781.
  • Make _mosquitto_mid_generate() thread safe. Closes #463479.