As a connoisseur of vulnerability disclosures and avid vulnerability collector, I am always interested in analysis of the disclosure landscape. That typically comes in the form of reports that analyze a data set (e.g. CVE/NVD) and draw conclusions. This seems straight-forward but it isn’t. I have written about the varied problems with such analysis many times in the past and yet, companies that don’t operate in the world of vulnerability databases still decide to play in our mud puddle. This time is the company Redscan, who I don’t think I had heard of, doing analysis on NVD data for 2020. Risk Based Security wrote a commentary on their analysis, to which I contributed, but I wanted to keep the party going over here with a few more personal comments. Just my opinions here, as a more outspoken critic on the topic, and where I break from the day job.
I am going to focus on one of my favorite topics; vulnerability tourists. People that may be in the realm of Information Security, but don’t specifically operate day-to-day in the world of vulnerability disclosures, and more specifically to me, vulnerability databases (VDBs). For this blog, I am just going to focus on a few select quotes that made me double-take. Read on after waving to Tourist Lazlo!
“The NVD tracks CVEs logged by NIST since 1988, although different iterations of the NVD account for some variation when comparing like-for-like results over time.”
There’s a lot to unpack here, most of it wrong. First, the NVD doesn’t track anything; they are spoon-fed that data from MITRE, who manages the CVE project. Second, NIST didn’t even create NVD until over five years after CVE started. Third, CVE didn’t track vulnerabilities “since 1988”; they cherry-picked some disclosures from before 1999, when they started, and why CVE IDs start with ‘1999’. Fourth, there was only one different iteration of NVD, that was their ICAT “CVE Metabase” that ran the first year of CVE basically. According to Peter Mell, who created it, said that after starting as its own vulnerability website, “ICAT had become an archival tool for CVE standard vulnerabilities and was only updated every three or four weeks”. Then in 2005 the site relaunched with a new focus and timely updates from CVE. Despite this quote, later in their report they produce a chart that tries to show an even comparison from 1988 to 2020 despite saying it went through iterations and despite not understanding CVSS.
“The growth is also likely attributable to an increase in the number of CVE Numbering Authorities (CNAs) – of which there are now more than 150 worldwide with the power to create and publish CVEs.”
The growth in disclosures aggregated by CVE is a lot more complicated than that, and the increase in CNAs I doubt is a big factor. Of course, they say this and don’t cite any evidence despite CVE now showing who the assigning CNA was (e.g. CVE-2020-2000 is Palo Alto Networks). The data is there if you want to make that analysis but it isn’t that easy since it isn’t included in the NVD exports. That means it requires some real work scraping the CVE website since they don’t include it in their exports either. Making claims without backing them up when the data is public and might prove your argument is not good.
“Again, this is a number that will concern security teams, since zero interaction vulnerabilities are famously difficult to detect and have the potential to cause significant damage.”
This makes me think that Redscan should invent a wall, perhaps made of fire, that could detect and prevent these attacks! Or maybe a system that is designed to detect intrusions! Or even one that can prevent intrusions! This quote is one that is truly baffling because it doesn’t really come with an explanation as to what they mean, and I hope they mean something far different than what this sounds like. I hope this isn’t a fear tactic to make readers think that their managed detection service is needed. Quite the opposite; anyone who says the above probably should not be trusted to do your attack detection.
This chart heading is one of many signs that Redscan doesn’t understand CVSS at all. For a “worst of the worst” vulnerability they got several attributes right but end up with “Confidentiality [High]”. The vulnerability they describe would only be CVSSv2 7.8 (AV:N/AC:L/Au:N/C:C/I:N/A:N) and CVSSv3.1 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N). That is not the worst. If it ‘highly’ impacts confidentiality, integrity, and availability then that becomes the worst of the worst, becoming CVSSv2 10.0 and CVSSv3.1 9.8 or 10.0 depending on scope. It’s hard to understand how a security company gets this wrong until you read a bit further where they say they “selected the very ‘worst’ option for every available metric.” My gut tells me they didn’t realize you could toggle ‘High’ for more than one impact and confidentiality is the first listed.
“It is also important to note that these numbers may have been artificially reduced. Tech giants such as Google and Microsoft have to do a lot to maintain their products and services day-to-day. It is common for them to discover vulnerabilities that are not being exploited in the wild and release a quick patch instead of assigning a CVE. This may account for fewer CVEs with a network attack vector in recent years.”
This is where general vulnerability tourism comes in as there is a lot wrong here. Even if you don’t run a VDB you should be passingly familiar with Microsoft advisories, as an example. Ever notice how they don’t have an advisory with a low severity rating? That’s because they don’t publish them. Their advisories only cover vulnerabilities at a certain threshold of risk. So that means that the statement above is partially right, but for the wrong reason. It isn’t about assigning a CVE, it is about not even publishing the vulnerability in the first place. Because they only release advisories for more serious issues, it actually skews their numbers to include more remote vulnerabilities, not less, primarily on the back of “remote” issues that require user interaction such as browser issues or file parsing vulnerabilities in Office.
This quote also suggests that exploitation in the wild is a bar for assigning a CVE, when it absolutely is not. It might also be a surprise to a company like Redscan, but there are vulnerabilities that are disclosed that never receive a CVE ID.
“Smart devices designed for the mass market often contain a worrying number of vulnerabilities due to manufacturer oversight. Firmware within devices is often used by multiple vendors, meaning that any vulnerabilities in this software has the potential to result in lots of CVEs.”
Wrong again, sometimes. If it is known to be the same firmware used in multiple devices, it gets one CVE ID. The only time there are additional IDs assigned is when multiple disclosures don’t positively ID the root cause. When three disclosures attribute the same vulnerability to three different products, it stands to reason there will be three IDs. But it isn’t how CVE is designed because it artificially inflates numbers, and that is the game of others.
“The prevalence of low complexity vulnerabilities in recent years means that sophisticated adversaries do not need to ‘burn’ their high complexity zero days on their targets and have the luxury of saving them for future attacks instead.”
“It is also encouraging that the proportion of vulnerabilities requiring high-level privileges has been on the increase since 2016. This trend means that cybercriminals need to work harder to conduct their attacks.”
So which is it? When providing buzz-quote conclusions such as these, that are designed to support the data analysis, they shouldn’t contradict each other. This goes back to what I have been saying for a long time; vulnerability statistics need qualifications, caveats, and explanations.
“Just because a vulnerability is listed in the NVD as hard to exploit doesn’t mean that attackers aren’t developing PoC code to exploit it. The key is to keep up with what’s happening in the threat landscape and respond accordingly.”
I’ll end here since this is a glowing endorsement for why vulnerability intelligence has to be more evolved than what CVE and NVD are offering. Part of the CVSS specifications include Temporal scoring and one of those attributes is Exploit Code Maturity. This is designed to specifically address the problem above; that knowing the capability of potential attackers matters. With over 21,000 vulnerabilities disclosed last year, organizations are finding that just patching based on the CVSSv3 base score isn’t enough. Sure, you patch the 10.0 / 9.8 since those are truly the worst-of-the-worst, and you patch the 9.3 / 8.8 since any random email might carry a payload. Then what? If all things are equal between vulnerabilities that impact your organization you should look to see if a patch is available (also covered by Temporal score) and if an exploit is available.
Numeric scores are not enough, you have to understand the context behind them. That CVSSv2 remote information disclosure that partially affects confidentiality by disclosing an admin password is only a 5.0. Score it under CVSSv3 and you are looking at a 9.8 because it immediately leads to privilege escalation which is factored in under that system. Heartbleed was a CVSSv2 5.0 with a functional exploit and available patch; look what hell that brought upon us. If you aren’t getting that type of metadata, reconsider your choice of vulnerability intelligence.