From Nexcess:
On June 23, Nexcess will apply an important update to libcurl on your server in the Eastern United States between 22:00 and 02:00 in the time zone local for your server. The libcurl update addresses the following concern: Previously, versions 1.1 and 1.2 of the TLS protocol were disabled by default in libcurl. Consequently, clients were required to explicitly enable these TLS versions in utilities based on libcurl in order to allow these utilities to securely communicate with servers that do not accept SSL 3.0 and TLS 1.0 connections. With this update, TLS 1.1 and TLS 1.2 are no longer disabled by default in libcurl. Clients can, however, explicitly disable them through the libcurl API. During this maintenance period, your site may experience a brief service disruption while the PHP-FPM service is restarted on the server. We anticipate restarting the service will take less than a few minutes. We apologize for the service disruption, and will work hard to ensure that the outage is as short as possible