Security Experts:

Cloudflare Finds No Evidence of "Cloudbleed" Exploitation

Cloudflare informed customers on Wednesday that it has found no evidence of the recently discovered memory leak being exploited for malicious purposes before it was patched.

The bug was discovered on February 17 by Google Project Zero researcher Tavis Ormandy. The expert jokingly considered the idea of calling it “Cloudbleed” due to some similarities to HeartBleed and the name stuck.

Cloudflare determined that the bug caused its edge servers to run past the end of a buffer and return memory that contained potentially sensitive information, including cookies and authentication tokens. Ormandy also found that the leaked data included passwords, encryption keys, private messages from dating sites, chat messages, IP addresses and HTTPS requests.

The flaw was introduced in September 2016, but it had the greatest impact between February 13 and February 18, when one in every 3.3 million requests going through Cloudflare’s systems may have resulted in memory leakage. The bug itself was addressed within hours, but it took several days to contain the incident due to the fact that leaked data had been cached by search engines.

In a lengthy blog post published on Wednesday, Cloudflare co-founder and CEO Matthew Prince said that while this was “an extremely serious bug” with a potentially massive impact, an analysis of the logs had turned up no evidence of malicious exploitation. Prince also pointed out that a vast majority of customers were not impacted.

“If a hacker were aware of the bug before it was patched and trying to exploit it then the best way for them to do so would be to send as many requests as possible to a page that contained the set of conditions that would trigger the bug. They could then record the results. Most of what they would get would be useless, but some would contain very sensitive information,” Prince said.

“The nightmare scenario we have been worried about is if a hacker had been aware of the bug and had been quietly mining data before we were notified by Google's Project Zero team and were able to patch it,” he added.

While Cloudflare’s investigation into the Cloudbleed incident continues, to date it has not identified any instances where the leaked memory included passwords, payment card numbers, customer encryption keys, or health records.

It’s worth pointing out that Ormandy, who believed CloudFlare’s initial blog post on Cloudbleed downplayed the risk, did report finding passwords in the leaked data.

“It is not correct to conclude that no passwords, credit cards, health records, social security numbers, or customer encryption keys were ever exposed,” Prince said. “However, if there was any exposure, based on the data we’ve reviewed, it does not appear to have been widespread. We have also not had any confirmed reports of third parties discovering any of these sensitive data types on any cached pages.”

For users who are concerned that their data may have been exposed, a list of potentially affected websites and a simple Chrome app for Mac have been made available.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.