Also the websocketpp deflate code is very new, so it might be a novel bug in websocketpp. A quick run-through of the websocketpp issue tracker shows some known race condition crash bugs in websocketpp [1] [2] [3] and it is not out of the realm of possibility that one of these leads to a use-after-free. Some of these bugs are TLS only, so it is possible that disabling TLS fixes the issue.
[1] https://github.com/zaphoyd/websocketpp/issues/459
[2] https://github.com/zaphoyd/websocketpp/issues/451
[3] https://github.com/zaphoyd/websocketpp/issues/336
[1] https://github.com/zaphoyd/websocketpp/issues/459
[2] https://github.com/zaphoyd/websocketpp/issues/451
[3] https://github.com/zaphoyd/websocketpp/issues/336
