OpenSSL 'high' severity flaw just a puny DoS risk

Is that all you’ve got, ClientHello? I put on my brown trousers for this?

OpenSSL patched a “high” severity flaw as part of a patch batch on Thursday that turned out to be nowhere near as scary as widely feared.

Fortunately, fears the software update might address another Heartbleed have been confounded. The worst of the flaws – dubbed ClientHello (CVE-2015-0291) – is simply a DoS risk, as an advisory from the developers explains.

If a client connects to an OpenSSL 1.0.2 server and renegotiates with an invalid signature algorithms extension a NULL pointer dereference will occur. This can be exploited in a DoS attack against the server.

This issue affects OpenSSL version: 1.0.2. OpenSSL 1.0.2 users should upgrade to 1.0.2a.

The other “high” (the highest severity classification of flaw in the OpenSSL world) vulnerability in the batch turned up to refer to an upgrade in severity in an RSA export ciphersuite patched in January. Initially classified as low, the vuln is now being treated as a “high” risk because it affected more systems than previously thought.

The remaining 12 advisories cover bugs that are rated as “moderate” or below.

Rapid7’s global security strategist, Trey Ford, commented: “Fourteen OpenSSL vulnerabilities were announced and addressed this morning. Two specific issues were classified as High Severity, one exposing the service to what appears to be an easy-to-execute Denial of Service attack; the other exposing the surprisingly common RSA export cipher suites to ‘man in the middle’ attacks. Incidentally, the highest severity issue (a crash via NULL pointer dereference) only affects version 1.0.2, and many users are still on versions 0.9.8 and 1.0.1.”

OpenSSL is widely deployed and attacks based on the vulns are likely, Ford warned. “We expect to see corresponding attack code quickly built by those reverse engineering the published patches – steps to push these fixes to net exposed systems should be prioritised. Export ciphers are overdue for retirement, and organisations using them should looks for ways to upgrade to more stringent encryption standards.”

Brown alert

The security world had to change its trousers after developers warned that they had a big release with a “high” severity bug coming.

Another easy-to-exploit flaw like Heartbleed was feared, as the industry feared the worst. Time to map systems, stock up on supplies and predict the worst-case scenario – a remote code injection risk, perhaps one that affected a lot of systems and, worse yet, was easy to exploit.

Instead, what happened is the IT equivalent of preparing for a Black Sabbath gig, complete with Ozzy Osbourne biting off a bat’s head, only to be treated be an a cappella set featuring Lionel Ritchie instead.

Denial of service (DoS) attacks present a system crash risk and are nothing to sniff at, but the feared RCE vuln would have been so much more dangerous. Were researchers pleased? Relieved? Hell no, they’ve already started complaining about the whole episode getting over-hyped.

Security researcher Space Rogue summed up the feeling of quite of few: “So I had stomach knots all week for a DoS and a upgrade of Freak? really?“

OpenSSL has had a fair few security issues of late but that shouldn’t be taken as a sign its more insecure than other crypto platforms, according to Ivan Ristic.

“It seems fashionable to bash OpenSSL, but remember that all major SSL/TLS stacks have a poor security record,” the software engineer and founder of SSL Labs said in a Twitter update. ®

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