How to prioritize vulnerabilities
Last reviewed
To prioritize vulnerabilities effectively, combine three signals instead of relying on one. Fix CISA KEV entries first because exploitation is confirmed, then rank the rest by EPSS likelihood and CVSS severity, escalating items that are both highly likely to be exploited and high impact. Add asset exposure and business context on top. Frameworks like SSVC formalize this decision tree.
Why prioritization matters
Most organizations discover far more vulnerabilities than they can ever patch. Sorting by CVSS severity alone floods the queue with critical findings that may never be attacked, while genuinely exploited flaws wait their turn. Effective prioritization is about spending limited remediation effort where it reduces the most real risk.
The modern, risk-based approach blends three independent signals: confirmed exploitation (CISA KEV), predicted likelihood of exploitation (EPSS), and potential impact (CVSS). Each answers a different question, and together they produce a far sharper ranking than any one of them alone.
The three core signals
| Signal | Question it answers | How to use it |
|---|---|---|
| CISA KEV | Is it being exploited right now? | Hard override: patch KEV entries first. |
| EPSS | How likely is exploitation soon? | Rank the remaining backlog by probability. |
| CVSS | How bad is the impact if exploited? | Weigh severity and blast radius. |
A practical workflow
A simple, defensible order of operations works for most teams.
- Step 1: Patch anything in your environment that appears on the CISA KEV catalog, regardless of its CVSS score, by the relevant due date.
- Step 2: Among the rest, escalate vulnerabilities with both a high EPSS probability and a high CVSS severity, since they are both likely to be attacked and damaging.
- Step 3: Use EPSS to triage the long tail, deprioritizing high-CVSS findings with near-zero EPSS until capacity allows.
- Step 4: Layer in asset context: internet exposure, data sensitivity, and business criticality can promote an otherwise lower-ranked item.
- Step 5: Re-run the ranking regularly, because EPSS updates daily and KEV grows as new exploitation is confirmed.
SSVC as a decision framework
If you want a more formal structure than a sorted list, the Stakeholder-Specific Vulnerability Categorization (SSVC) framework is a useful alternative. SSVC is a decision tree, developed by CISA and Carnegie Mellon's SEI, that routes each vulnerability into an outcome such as Track, Track-star, Attend, or Act.
SSVC uses inputs like exploitation status (which maps neatly onto KEV and EPSS), technical impact, and the mission and well-being impact on the organization. It is a way to make the same severity, likelihood, and context judgments explicit and repeatable rather than ad hoc.
Common mistakes to avoid
- Relying only on CVSS, which overloads the queue with severe-but-unexploited findings.
- Treating EPSS as a severity score; it estimates likelihood, not impact.
- Assuming a CVE absent from the KEV is safe, when it may simply lack confirmed evidence.
- Prioritizing once and never re-running it, even though EPSS and KEV change daily.
Keep exploring
- What is EPSS?The likelihood signal in your prioritization.
- What is the CISA KEV?The confirmed-exploitation override.
- CVSS vs EPSSWhy you need both severity and likelihood.
- EPSS vs KEVPredicted versus confirmed exploitation.
- CVSS calculatorCompute and interpret a CVSS severity vector.
- What is Metasploit?The framework for authorized penetration testing.
- SAST vs DASTStatic versus dynamic application security testing.
Frequently asked questions
- What should I patch first?
- Patch vulnerabilities in your environment that appear on the CISA KEV catalog first, because exploitation is confirmed. Then rank the rest by EPSS likelihood and CVSS severity.
- Can I prioritize using CVSS alone?
- You can, but it is inefficient. CVSS measures impact, not likelihood, so it surfaces many severe vulnerabilities that are never attacked. Adding EPSS and KEV sharpens the ranking dramatically.
- How do CVSS, EPSS, and KEV fit together?
- KEV confirms exploitation (patch first), EPSS predicts likelihood (rank the backlog), and CVSS measures impact (weigh consequences). Combining all three gives a risk-based priority order.
- What is SSVC?
- SSVC, Stakeholder-Specific Vulnerability Categorization, is a decision-tree framework from CISA and the SEI that formalizes prioritization using exploitation status, impact, and organizational context.
- How often should I re-prioritize?
- Frequently. EPSS scores update daily and the KEV catalog grows as exploitation is confirmed, so a ranking that was correct last week may be stale today.