Cloudbleed: Big web brands leaked crypto keys, personal secrets thanks to Cloudflare bug

Iain Thomson reports:

Big-name websites leaked people’s private session keys and personal information into strangers’ browsers, due to a Cloudflare bug uncovered by Google security researchers.

Cloudflare helps companies spread their websites and online services across the internet. Due to a programming blunder, for several months Cloudflare’s systems slipped random chunks of server memory into webpages, under certain circumstances. That means if you visited a website powered by Cloudflare, you may have ended up getting chunks of someone else’s web traffic hidden in your browser page.

Read more on The Register.

Related: Cloudflare’s incident report.

Update: Here’s the email notification I received this morning since I am a Cloudflare customer:

Thursday afternoon, we published a blog post describing a memory leak caused
by a serious bug that impacted Cloudflare’s systems. If you haven’t yet, I
encourage you to read that post on the bug:

While we fully resolved the bug within hours of it being reported to us, there
was an ongoing risk that some of our customers’ sensitive information would
still be available through third party caches, such as the Google search

Over the last week, we’ve worked with these caches to discover what customers
may have had sensitive information exposed and ensure that the caches are
purged. We waited to disclose the bug publicly until after these caches could
be cleared in order to mitigate the potential impact and ability of malicious
individuals to exploit any leaked data.

In our review of these third party caches, we discovered data on approximately
150 of Cloudflare’s customers across our Free, Pro, Business, and Enterprise
plans. You are receiving this email because you are one of the customers where
our team was able to identify data that was leaked due to the bug and stored
in one of these third party caches.

While the third party cache where your data was found has subsequently been
cleared and should no longer be publicly available, we wanted to share with
you exactly what we found so you can understand any the impact. We have a
technical team standing by to review the data with you and answer any
questions you have. To setup a call with this team, please email
[email protected] with the subject: “HIGH PRIORITY: Parser Bug.”

While we have yet to discover any instance of the bug being exploited, we
recommend you invalidate and reissue any persistent secrets, such as long
lived session identifiers, tokens or keys. Due to the nature of the bug,
customer SSL keys were not exposed and do not need to be rotated. We will take
the time to review your individual circumstances based on what we’ve found,
answer any questions you have, and work with you to ensure you understand how
you can best protect yourself and your customers.

In the meantime, if you have any questions, please don’t hesitate to reach out
to me directly.

Matthew Prince
Cloudflare, Inc.
Co-founder and CEO

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