Cloudflare bug leaks personal info from 120,000 sites

Hackers are not exploiting 'Cloudbleed' flaw, says CTO

Cloudflare has been leaking personal information, passwords and software keys from over 120,000 sites and services onto the internet, the company has revealed.

The leak was due to a bug in the systems of the company, which offers anti-DDoS and CDN services for around six million websites, and affected companies such as Uber, OKCupid, Fitbit and more.

Discovered by Google security researcher Tavis Ormandy, the bug - which has already been dubbed 'Cloudbleed' after the Heartbleed openSSL vulnerability discovered in 2014 - is apparently a buffer overflow issue and has been blamed on malformed HTML code.

"In some unusual circumstances," Cloudflare CTO John Graham-Cumming wrote in a blog post detailing the issue, "our edge servers were running past the end of a buffer and returning memory that contained private information such as HTTP cookies, authentication tokens, HTTP POST bodies, and other sensitive data. And some of that data had been cached by search engines."

Advertisement - Article continues below
Advertisement - Article continues below

In layman's terms, this meant that users visiting Cloudflare-hosted sites could wind up with data from other sites embedded in their browser. So, someone visiting the Fitbit site could end up accidentally gathering data from another person's OKCupid activity.

The leak was most active from 13 February to 18 February, Graham-Cumming said, affecting around 120,000 sites per day. It may also have been active since 22 September 2016.

Graham-Cumming has said that the issue is now fixed and cached data largely removed from search engines such as Google, adding that he does not believe that the leaked information has been exploited by hackers.

Ormandy kept a running log of the incident, from initial discovery all the way to resolution and public disclosure, including examples of some of the data that was being exposed by the issue.

"We fetched a few live samples, and we observed encryption keys, cookies, passwords, chunks of POST data and even HTTPS requests for other major cloudflare-hosted sites from other users," he wrote. "We've discovered (and purged) cached pages that contain private messages from well-known services, PII from major sites that use Cloudflare, and even plaintext API requests from a popular password manager that were sent over https (!!)."

"The examples we're finding are so bad, I cancelled some weekend plans to go into the office on Sunday to help build some tools to cleanup. I've informed Cloudflare what I'm working on. I'm finding private messages from major dating sites, full messages from a well-known chat service, online password manager data, frames from adult video sites, hotel bookings. We're talking full https requests, client IP addresses, full responses, cookies, passwords, keys, data, everything."

Advertisement - Article continues below

While Cloudflare says it's confident that the information is not being exploited, some security experts are warning that accounts hosted on any site that uses Cloudflare could be compromised, and that users may want to change their account details and passwords.

Image credit: Tavis Ormandy

Featured Resources

How inkjet can transform your business

Get more out of your business by investing in the right printing technology

Download now

Journey to a modern workplace with Office 365: which tools and when?

A guide to how Office 365 builds a modern workplace

Download now

Modernise and transform your sales organisation

Learn how a modernised sales process can drive your business

Download now

Your guide to managing cloud transformation risk

Realise the benefits. Mitigate the risks

Download now


internet security

Avast and AVG extensions pulled from Chrome

19 Dec 2019

Google confirms Android cameras can be hijacked to spy on you

20 Nov 2019

How to protect against a DDoS attack

25 Oct 2019
data breaches

Ex-Equifax CIO to serve four months for insider trading

2 Jul 2019

Most Popular


How to use Chromecast without Wi-Fi

5 Feb 2020
artificial intelligence (AI)

AI identifies 11 earth-bound asteroids

18 Feb 2020
operating systems

How to fix a stuck Windows 10 update

12 Feb 2020
Business operations

HP shareholders invited to come dine with Xerox

17 Feb 2020