Lack of CSPRNG Threatens WordPress Sites

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WordPress has become a huge target for attackers and vulnerability researchers, and with good reason. The software runs a large fraction of the sites on the Internet and serious vulnerabilities in the platform have not been hard to come by lately. But there’s now a new bug that’s been disclosed in all versions of WordPress that may allow an attacker to take over vulnerable sites.

The issue lies in the fact that WordPress doesn’t contain a cryptographically secure pseudorandom number generator. A researcher named Scott Arciszewski made the WordPress maintainers aware of the problem nearly eight months ago and said that he has had very little response.

“On June 25, 2014 I opened a ticked on WordPress’s issue tracker to expose a cryptographically secure pseudorandom number generator, since none was present,” he said in an advisory on Full Disclosure.

“For the past 8 months, I have tried repeatedly to raise awareness of this bug, even going as far as to attend WordCamp Orlando to troll^H advocate for its examination in person. And they blew me off every time.”

The consequences of an attack on the bug would be that the attacker might be able to predict the token used to generate a new password for a user’s account and thus take over the account. Arciszewski has developed a patch for the problem and published it, but it has not been integrated into WordPress. Since the public disclosure, he said he has had almost no communication from the WordPress maintainers about the vulnerability, save for one tweet from a lead developer that was later deleted.

Arciszewski said he has not developed an exploit for the issue but said that an attacker would need to be able to predict the next RNG seed in order to exploit it.

“There is a rule in security: attacks only get better, never worse. If this is not attackable today, there is no guarantee this will hold true in 5 or 10 years. Using /dev/urandom (which is what my proposed patch tries to do, although Stefan Esser has highlighted some flaws that would require a 4th version before it’s acceptable for merging) is a serious gain over a userland RNG,” he said by email.

But, as he pointed out, this kind of bug could have a lot of value for a lot of attackers.

“WordPress runs over 20% of websites on the Internet. If I were an intelligence agency (NSA, GCHQ, KGB, et al.) I would have a significant interest in hard-to-exploit critical WordPress bugs, since the likelihood of a high-value target running it as a platform is pretty significant. That’s not to say or imply that they knew about this flaw! But if they did, they probably would have sat on it forever,”Arciszewski said.

WordPress officials did not respond to questions for this story before publication.

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