OpenSSL Patches for 'Boring' Certificate Risk

By Sean Michael Kerner  |  Posted 2015-07-09 Print this article Print
OpenSSL Patches

The open-source OpenSSL cryptographic library project came out today with a high-severity security advisory and patched a single vulnerability, identified as CVE-2015-1793. OpenSSL is a widely used technology that helps to enable Secure Sockets Layer/Transport Layer Security (SSL/TLS) encryption for Web data transport for both servers and end-user devices.

The CVE-2015-1793 advisory, titled "Alternative chains certificate forgery," is a non-trivial risk that, if exploited, could enable an attacker to impersonate a legitimate digital security certificate. The SSL/TLS digital certificate asserts the identity and authenticity of a given site and connection.

"During certificate verification, OpenSSL (starting from version 1.0.1n and 1.0.2b) will attempt to find an alternative certificate chain if the first attempt to build such a chain fails," the OpenSSL advisory warns. "An error in the implementation of this logic can mean that an attacker could cause certain checks on untrusted certificates to be bypassed, such as the CA [Certificate Authority] flag, enabling them to use a valid leaf certificate to act as a CA and "issue" an invalid certificate."

What that means is that the integrity of the SSL/TLS authentication scheme that underpins the security of the Internet as we know it could be bypassed—that is, if the attacker knows about this flaw and is able to exploit it.

The CVE-2015-1793 issue is not a zero-day flaw, though, and it already has a patch, thanks to Google's efforts. The OpenSSL project's advisory noted that the CVE-2015-1793 vulnerability was reported by Google security researchers Adam Langley and David Benjamin on June 24. Those two researchers are associated with Google's BoringSSL initiative, first announced in June 2014.

Google is no stranger to OpenSSL and, in fact, was one of the original groups that discovered the Heartbleed SSL flaw in 2014. Google is also a large user of OpenSSL, which is where the BoringSSL effort comes into play. BoringSSL is actually Google's fork of OpenSSL, with Google contributing its changes (in this case, a security fix) upstream to the OpenSSL project.

As the CVE-2015-1793 issue is brand new, I haven't see any weaponized exploits for it (yet) in Metasploit or other commonly used penetration toolkits. From my own cursory understanding of how OpenSSL works and the CVE-2015-1793 vulnerability disclosure, I don't think it will take very long for proof-of-concept code to emerge to weaponize this flaw.

So the message here is clear: The patch is out, and it's time for all OpenSSL users to update. That's easier said than done, of course. For server users on the major Linux operating system vendors, it's a simple matter of updating, since the packaged code is already in the Linux distribution repositories. Not all server administrators update rapidly, though, which will leave a window of risk. Then there are the systems that don't have patches available (yet), like Apple's OS X and multiple variants of Android, which will take time.

Time and again, I see reports from vendors that indicate that unpatched, known vulnerabilities are the root cause of breaches. Time will tell what the true impact of CVE-2015-1793 will be, for those that don't patch quickly.

Sean Michael Kerner is a senior editor at eWEEK and Follow him on Twitter @TechJournalist. |

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