The ISC has received several requests asking us to weigh in on the ramifications of the Cloudflare data leak, also being referred to by some as CloudBleed.

The short version of the vulnerability is that in rare situations, a bug in Cloudflare's edge servers could be triggered, which would cause a buffer overrun to occur. When these buffer overruns occurred, random data would be returned in the replies from the Cloudflare servers. Private chat messages, user logins and passwords, and many other bits of data were found in the random data. This data would be data from any of Cloudflare's customer applications, which is a very big list of some of the most popular sites on the Internet.  Potentially over 4 million domains. (Partial list of popular sites and the full list are available here).  Most seriously, these pages, containing random data, were cached to Google's search results (those results have now been scrubbed of Cloudflare data).  

It is believed that this vulnerability was present from 22 Sept, 2016 until 18 Feb. 2017.

What does this mean to you?  Unfortunately, the data leak means that this needs to be treated as another data breach. If you have an account on any Cloudflare hosted application, which we almost certainly all do, it is time to go and change your passwords.  I would also strongly recommend that you use this as an opportunity to enable 2-factor authentication on any application that supports it.

UPDATE 20170224 17:45 UTC: It appears Cloudflare customers have started sending out password change requests. I just received my first a few minutes ago.

-- Rick Wanner MSISE - rwanner at isc dot sans dot edu - http://namedeplume.blogspot.com/ - Twitter:namedeplume (Protected)