If you’re running port scans on your servers and wondering what to do with all those open ports you’ve discovered, you’re only halfway there. The real question isn’t just ”what ports are open?” but ”what vulnerabilities am I exposing?” That’s where CVE databases become absolutely critical for anyone serious about port security.
I learned this the hard way a few years back when I found port 8080 open on a web server. I thought, ”well, it’s just an alternate HTTP port, no big deal.” Turns out it was running an outdated version of Apache Tomcat with several known CVEs that could have given attackers remote code execution. The port scan showed me the door was open, but the CVE database showed me someone had already picked the lock.
What Exactly Are CVE Databases?
CVE stands for Common Vulnerabilities and Exposures, and it’s essentially a standardized naming system for known security vulnerabilities. When security researchers discover a flaw in software, it gets assigned a unique CVE identifier like CVE-2024-1234. This creates a common language that security professionals worldwide can use to discuss and track vulnerabilities.
The main CVE database is maintained by MITRE Corporation and sponsored by the US Department of Homeland Security, but there are several other important databases you should know about. The National Vulnerability Database (NVD) by NIST adds additional analysis and severity scores to each CVE. Then there are specialized databases like Exploit-DB that focus on publicly available exploits, and vendor-specific databases from companies like Red Hat, Ubuntu, and Debian.
How CVE Information Connects to Port Scanning
Here’s where it gets practical. When you scan a port and find it open, you typically get three pieces of information: the port number, the service running on it, and often the software version. For example, you might find port 22 open running OpenSSH version 7.4.
That version number is your key to the CVE database. You can search for ”OpenSSH 7.4 CVE” and discover all known vulnerabilities for that specific version. Some might be low-risk information disclosure issues, while others could be critical remote execution flaws. Without checking CVE databases, you’re essentially driving blind – you know the road exists, but not whether there’s a cliff ahead.
Reading and Understanding CVE Entries
When you look up a CVE, you’ll typically see several key pieces of information. The CVSS score (Common Vulnerability Scoring System) rates severity from 0-10, with 9.0+ being critical. Pay attention to this, but don’t rely on it exclusively.
The description tells you what the vulnerability actually does. Attack vector information shows whether it can be exploited remotely or requires local access. Required privileges indicate if an attacker needs authentication first. And crucially, the ”exploitability” metric tells you if working exploit code is publicly available.
I always check the publication date too. A ten-year-old critical CVE might sound scary, but if it’s been patched for years and you’re running current software, it’s not your immediate concern. Conversely, a medium-severity CVE from last week might deserve urgent attention if patches aren’t available yet.
Practical Workflow for Port Security Assessment
Start by running your port scan and documenting every open port with its service and version. I typically use nmap with version detection enabled, which gives you the detailed information you need.
Next, create a spreadsheet or use a vulnerability management tool to track findings. For each service, search the NVD database using the exact version number. Don’t just search for the service name alone – ”Apache” returns thousands of results, but ”Apache 2.4.41” narrows it down considerably.
Prioritize based on three factors: CVSS score, whether the port is internet-facing, and whether exploit code exists. A critical CVE on an internal-only management port is different from one on your public web server.
Common Mistakes People Make
The biggest mistake I see is ignoring low and medium severity CVEs. Yes, critical vulnerabilities deserve immediate attention, but attackers often chain together multiple lower-severity issues to achieve their goals. A medium-severity information disclosure vulnerability might reveal system details that make a separate attack much easier.
Another myth is that closed-source or obscure software is safer because there are fewer CVEs. That’s backwards thinking. Fewer CVEs often means fewer people are looking for vulnerabilities, not that they don’t exist. Popular software gets scrutinized more, which actually makes the CVE database more complete and useful.
Don’t assume that because a port is ”supposed” to be open, it’s automatically secure. Yes, port 443 needs to be open for HTTPS, but if you’re running a vulnerable version of your web server software, that open port becomes your weakest link.
Tools That Integrate CVE Checking
While manual CVE lookup works, several tools automate this process. OpenVAS and Nessus can scan ports and automatically cross-reference versions against CVE databases. For those on a budget, OWASP Dependency-Check works well for application-level vulnerabilities.
I’ve also had good results with custom scripts that parse nmap output and query the NVD API automatically. The API is free and relatively straightforward to use if you have basic programming skills.
Keeping Your CVE Knowledge Current
New CVEs are published constantly. Subscribe to security mailing lists for the specific software you run. The NVD has RSS feeds you can follow, and many Linux distributions have security announcement lists that highlight relevant CVEs with patch information.
Set a recurring calendar reminder to re-scan your ports and re-check CVE databases quarterly at minimum. For critical infrastructure, monthly is better. The security landscape changes fast, and yesterday’s secure configuration might be today’s vulnerability.
Frequently Asked Questions
Do I need to fix every CVE I find? No. Prioritize based on exploitability, exposure, and business impact. Some CVEs require specific conditions that don’t apply to your environment.
What if my software version isn’t listed in the CVE database? That usually means no known vulnerabilities have been publicly disclosed yet. It doesn’t mean the software is perfectly secure, just that nothing is publicly known.
Are CVE databases complete? No. Zero-day vulnerabilities by definition aren’t in CVE databases yet. There’s always a lag between discovery and publication, and some vulnerabilities are never publicly disclosed.
The bottom line is this: port scanning without CVE database checks is like getting a medical test without understanding the results. The data is useless without context, and that context comes from understanding what vulnerabilities your open ports might expose.