static void conn_free(struct connectdata *conn)
{
  if(!conn)
    return;

  /* possible left-overs from the async name resolvers */
  Curl_resolver_cancel(conn);

  /* close the SSL stuff before we close any sockets since they will/may
     write to the sockets */
  Curl_ssl_close(conn, FIRSTSOCKET);
  Curl_ssl_close(conn, SECONDARYSOCKET);

  /* close possibly still open sockets */
  if(CURL_SOCKET_BAD != conn->sock[SECONDARYSOCKET])
    Curl_closesocket(conn, conn->sock[SECONDARYSOCKET]);
  if(CURL_SOCKET_BAD != conn->sock[FIRSTSOCKET])
    Curl_closesocket(conn, conn->sock[FIRSTSOCKET]);
  if(CURL_SOCKET_BAD != conn->tempsock[0])
    Curl_closesocket(conn, conn->tempsock[0]);
  if(CURL_SOCKET_BAD != conn->tempsock[1])
    Curl_closesocket(conn, conn->tempsock[1]);

#if !defined(CURL_DISABLE_HTTP) && defined(USE_NTLM) && \
    defined(NTLM_WB_ENABLED)
  Curl_ntlm_wb_cleanup(conn);
#endif

  Curl_safefree(conn->user);
  Curl_safefree(conn->passwd);
  Curl_safefree(conn->oauth_bearer);
  Curl_safefree(conn->options);
  Curl_safefree(conn->http_proxy.user);
  Curl_safefree(conn->socks_proxy.user);
  Curl_safefree(conn->http_proxy.passwd);
  Curl_safefree(conn->socks_proxy.passwd);
  Curl_safefree(conn->allocptr.proxyuserpwd);
  Curl_safefree(conn->allocptr.uagent);
  Curl_safefree(conn->allocptr.userpwd);
  Curl_safefree(conn->allocptr.accept_encoding);
  Curl_safefree(conn->allocptr.te);
  Curl_safefree(conn->allocptr.rangeline);
  Curl_safefree(conn->allocptr.ref);
  Curl_safefree(conn->allocptr.host);
  Curl_safefree(conn->allocptr.cookiehost);
  Curl_safefree(conn->allocptr.rtsp_transport);
  Curl_safefree(conn->trailer);
  Curl_safefree(conn->host.rawalloc); /* host name buffer */
  Curl_safefree(conn->conn_to_host.rawalloc); /* host name buffer */
  Curl_safefree(conn->secondaryhostname);
  Curl_safefree(conn->http_proxy.host.rawalloc); /* http proxy name buffer */
  Curl_safefree(conn->socks_proxy.host.rawalloc); /* socks proxy name buffer */
  Curl_safefree(conn->master_buffer);
  Curl_safefree(conn->connect_state);

  conn_reset_all_postponed_data(conn);

  Curl_llist_destroy(&conn->send_pipe, NULL);
  Curl_llist_destroy(&conn->recv_pipe, NULL);

  Curl_safefree(conn->localdev);
  Curl_free_primary_ssl_config(&conn->ssl_config);
  Curl_free_primary_ssl_config(&conn->proxy_ssl_config);

#ifdef USE_UNIX_SOCKETS
  Curl_safefree(conn->unix_domain_socket);
#endif

#ifdef USE_SSL
  Curl_safefree(conn->ssl_extra);
#endif
  free(conn); /* free all the connection oriented data */
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.