As of this morning we have observed 224 breaches related to CVE-2014-0160, the Heartbleed vulnerability. More than enough has been said about the technical details of the vulnerability, and our own Ryan Huber covered the details a few days ago. I want to talk about the vulnerability management implications of Heartbleed, because they are both terrifying and telling.
The Common Vulnerability Scoring System ranks CVE-2014-0160 as a 5.0/10.0. A good observer will note that the National Vulnerability Database is not all that comfortable with ranking the vulnerability that broke the internet a 5/10. In fact, unlike any other vulnerability in the system we’ve seen, there is an “addendum” in red text:
“CVSS V2 scoring evaluates the impact of the vulnerability on the host where the vulnerability is located. When evaluating the impact of this vulnerability to your organization, take into account the nature of the data that is being protected and act according to your organization’s risk acceptance. While CVE-2014-0160 does not allow unrestricted access to memory on the targeted host, a successful exploit does leak information from memory locations which have the potential to contain particularly sensitive information, e.g., cryptographic keys and passwords. Theft of this information could enable other attacks on the information system, the impact of which would depend on the sensitivity of the data and functions of that system.”
So what does this mean for your organization? How should you prioritize the remediation of Heartbleed vs other vulnerabilities? NVD’s answer is “think about what can be stolen.” The problem here is that the CVSS environmental metric, which is used to account for an organization’s particular environment, can only reduce the score. So we’re still stuck at a 5. Why?
CVSS is failing to take into account quite a few factors:
1. It’s a target of opportunity for attackers:
The amount of sites affected by the vulnerability is unfathomable – with broad estimates between 30-70% of the internet.
2. It’s being actively and successfully exploited on the Internet:
We are logging about 20 breaches every few hours. The rate of incoming breaches is also increasing, on April 10th, we were seeing 1-2 breaches an hour. Keep in mind this is just from the 30,000 businesses that we monitor - not 70% of the Internet.
3. It’s easy to exploit:
We already knew heartbleed was a big deal – this data isn’t changing anyone’s mind. The interesting bit, is that Heartbleed is not the only vulnerability to follow such a pattern. Of all the breached vulnerabilities in our database, Heartbleed is the fifth most breached (that is, most instances recorded) with a CVSS score of 5 or less.
The others that CVSS is missing the boat on, in order of descending breach volume, are:
1. CVE-2001-0540 - Score: 5.0
2. CVE-2012-0152 - Score: 4.3
3. CVE-2006-0003 – Score: 5.1
4. CVE-2013-2423 - Score: 4.3
Two of these are terminal denial of service, and two of these are remote code executions. The common thread is that all of these have a network access vector and require no authentication, all of these have exploits available, affect a large number of systems and are currently being breached.
Heartbleed IS a big deal. But it’s not the only one – there are plenty of vulnerabilities which have received less press and are buried deep within the PCI requirements or CVSS-based prioritization strategies which are causing breaches, today. It’s important to check threat intelligence feeds for what’s being actively exploited, to think like an attacker and to have the same information an attacker has.
It’s also important to learn a lesson from this past week: while the press took care of this one, it won’t take care of a remote code execution on a specific version of windows that your organization happens to be running. Just don’t say it’s not a big deal when a breach occurs on a CVSS 4.3. You’ve been warned.