[Infowarrior] - Serious Cloudflare bug exposed a potpourri of secret customer data

[Richard Forno]

Serious Cloudflare bug exposed a potpourri of secret customer data

Service used by 5.5 million websites may have leaked passwords and authentication tokens.

Dan Goodin - 2/23/2017, 8:35 PM

Cloudflare, a service that helps optimize the security and performance of more than 5.5 million websites, warned customers today that a recently fixed software bug exposed a range of sensitive information that could have included passwords, and cookies and tokens used to authenticate users.

A combination of factors made the bug particularly severe. First, the leakage may have been active since September 22, nearly five months before it was discovered, although the greatest period of impact was from February 13 and February 18. Second, some of the highly sensitive data that was leaked was cached by Google and other search engines. The result was that for the entire time the bug was active, hackers had the ability to access the data in real-time, by making Web requests to affected websites, and to access some of the leaked data later by crafting queries on search engines.

"The bug was serious because the leaked memory could contain private information and because it had been cached by search engines," Cloudflare CTO John Graham-Cumming wrote in a blog post published Thursday. "We are disclosing this problem now as we are satisfied that search engine caches have now been cleared of sensitive information. We have also not discovered any evidence of malicious exploits of the bug or other reports of its existence."

The leakage was the result of a bug in an HTML parser chain Cloudflare uses to modify Web pages as they pass through the service's edge servers. The parser performs a variety of tasks, such as inserting Google Analytics tags, converting HTTP links to the more secure HTTPS variety, obfuscating email addresses, and excluding parts of a page from malicious Web bots. When the parser was used in combination with three Cloudflare features—e-mail obfuscation, server-side Cusexcludes, and Automatic HTTPS Rewrites—it caused Cloudflare edge servers to leak pseudo random memory contents into certain HTTP responses.

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https://arstechnica.com/security/2017/02/serious-cloudflare-bug-exposed-a-potpourri-of-secret-customer-data/