Vulnerability Prioritization & the Magic 8 Ball

COMMENTARY

Last month marks 25 years of operation for the CVE (Common Vulnerabilities and Exposures) program, launched in September 1999. It's difficult to imagine a world without CVEs. Much of the "vulnerability management" activities, before the CVE program became popular, relied on matching version numbers from remote scans and executing shady exploits found in dark places on the Internet to validate findings. We've come a long way when it comes to vulnerability tracking. Our journey has been fraught with peril, however, and we still have many challenges to overcome, including:

While the creation of formal tracking for vulnerabilities was huge for the industry, it wasn't until 2005 that we began to assign a severity rating using CVSS. This, too, is not without challenges, such as:

What Do We Do Now?

Given there are pros and cons to each of these programs whose intentions are to help organizations make informed risk-based decisions, how do we know what to patch first? Many will rely on one mechanism, likely CVSS, pick a magic number, and patch everything that scores above that magic number. The problem is this is a very limited view of the vulnerability world. Everything that needs to be patched will not have a high CVSS score, or even a low score for that matter. We can choose to follow one or more of the above frameworks, such as MITRE ATT&CK, CISA KEV, and EPSS. Following these individually can be tricky, and you'd miss pieces of the larger picture. If you only patched the CISA KEV, you'd miss out on select attacker techniques that don't deal with vulnerabilities and CVEs. A blended approach isn't a bad idea, but solely relying on guidance external to your organization is the equivalent of just shaking a Magic 8 Ball and using that as the guidance to patch.

What matters most when it comes to patching is the impact on your organization. My best advice is to identify the most critical parts of your business, tie that back to systems and applications, patch those first, and patch as much as you can on those systems.

Conclusion

Too often, I hear folks dismissing vulnerabilities that could be devastating for various reasons, such as "No one is attacking those vulnerabilities today," "I am not the target of nation-state-level attacks," and "An attacker would have to already be on the system." None of these things matter when a clever group of attackers is determined to be successful. They will target every weakness in your attack surface: hardware, firmware, and software, from bare metal all the way to the cloud. Pre-operating system attacks could render a system permanently damaged or inoperable, such as if an attacker were to gain access to the baseboard management controller (BMC) and cause an infinite reboot loop. Through low-level firmware attacks, malicious actors can permanently damage the hardware. Attackers can utilize the Unified Extensible Firmware Interface (UEFI) to bypass OS protections, be persistent on the system (think of ransomware that just won't go away), and allow attackers to be stealthy. At this point, every vulnerability is now available for exploit. 

Remediating vulnerabilities is a complex process, and several factors go into the decision as to whether or not to apply a patch, or thousands of patches to thousands of systems. As complex as this task may be, it's something we must continue to improve upon, or attackers will greatly benefit. Oh, and put down the Magic 8 Ball, please.