Some of the Internet's most visited websites that encrypt data with the SSL protocol are still susceptible to a recently announced vulnerability that could allow attackers to intercept and decrypt connections.
On June 5, developers of the widely used OpenSSL crypto library released emergency security patches to address several vulnerabilities, including one tracked as CVE-2014-0224 that could allow attackers to spy on encrypted connections if certain conditions are met.
Until a few years ago, full-session encryption via HTTPS (HTTP with SSL) was mainly used by financial, e-commerce and other sites dealing with sensitive information. However, the increasing use of mobile devices that often connect over insecure wireless networks, coupled with the past year's revelations of upstream bulk data collection by spy agencies, led to a large number of sites adding support for it.
OpenSSL is the most popular cryptographic library for implementing SSL/TLS support on Web servers.
In order to exploit CVE-2014-0224 to decrypt and modify SSL traffic, attackers would need to have a "man-in-the-middle" position between a client and a server that both use OpenSSL. Furthermore, the server would need to run an OpenSSL version from the 1.0.1 branch.
According to scans performed Thursday by Ivan Ristic, who runs the SSL Labs at security vendor Qualys, about 14 percent of sites monitored by the SSL Pulse project run a version of OpenSSL that allows exploiting the CVE-2014-0224 flaw.
The SSL Pulse project monitors the strength of SSL implementations on HTTPS-enabled sites from the list of top 1 million most visited sites as published by Internet statistics firm Alexa -- 154,406 sites as of June 2nd.
An additional 36 percent of websites from the SSL Pule data set run OpenSSL versions from the 0.9.x or 1.0.0 branches that also contain the flaw, but against which the exploit known so far doesn't work.
Those servers should be upgraded too because it's possible that there are other yet-to-be-discovered ways to exploit the problem, Ristic said in a blog post Friday.
The patching rate for CVE-2014-0224 does not appear to be as high as the one for Heartbleed, a more serious vulnerability revealed at the beginning of April that also affected OpenSSL clients and servers.
"The good news is that most browsers don't rely on OpenSSL, which means that most browser users won't be affected," Ristic said. "However, Android browsers do use OpenSSL and are vulnerable to this attack. Additionally, many command-line and similar programmatic tools use OpenSSL. A particularly interesting target will be various VPN products, provided they are based on OpenSSL (like, for example, OpenVPN)."
Website administrators who want to check if their servers are vulnerable to CVE-2014-0224 can use a free online testing tool developed by Qualys SSL Labs.