Here’s something to make you sit up and take notice: Amazon Web Services has notified customers that an “urgent patch” to many  EC2 hosts will start September 26 and continue through September 30.

This is according to a blog post by [company]RightScale[/company] CTO Thorsten Von Eicken and there’s more here on Hacker News and the AWS forum. RightScale helps customers monitor and manage their workloads in AWS and other clouds so it has a pretty good view into customer interactions with AWS, and vice versa.

Von Eicken wrote that [company]Amazon[/company] cloud users should know that if an instance is relaunched between now and the upgrade, they will not necessarily be connected to a patched host.

As he points out, Amazon is not very transparent about what the underlying issues, although he — and others — speculate that a security issue is the cause. It appears that T1, T2, M2, R3 and HS1 instance types are not impacted…