A critical security issue in the virtualization software Xen will become public July 26 and the Xen team has already informed Gandi of the necessary patches.
Since this announcement, we have already preemptively deployed the patches required to correct the issue. We have been monitoring the particular security flaw and have determined we will need to stop/start certain Xen VMs in order to assure that no further possible attack vector will remain.
We will be contacting the affected customers directly in order to allow them to sufficiently prepare for this stop/start and those of you who have not received any message from us are therefore not affected.
In order to minimize downtime and also to help minimize the impact in general, we would advise all affected to schedule a stop/start of their platforms yourselves sometime between now and the cutoff date of July 26, 2016.
Any affected VMs that you have not yet stopped and started again by 12:00 AM PDT July 26, 2016 (07:00 UTC), we will stop/start at some point between then and July 28 at 9:00 AM PDT (16:00 UTC). Please expect around 30 minutes of downtime per stop/start.
As always, if you have any questions or have any difficulties, please do not hesitate to contact our Customer care team.
Edit 7/21/16: Previously we used the term "reboot" instead of "stop/start." Rebooting isn't sufficient to apply the security patch. Your VM(s) need to be stopped and then started again in order for the patch to take effect.