You run a scan. It reports Apache 2.4.41 is vulnerable to a CVE from 2022. You check the server and it is fully patched. The scanner is not broken; the version string is lying to you, politely, because of how Debian and Ubuntu handle security fixes.
What backporting means
Linux distributions like Debian, Ubuntu, and RHEL do not always ship the latest upstream version of a package. Instead, they take a stable base version and apply only the security patches that affect it. That keeps systems stable while still fixing vulnerabilities. The problem for scanners is that the package version string often stays close to the original upstream release. A banner grab that sees Apache/2.4.41 cannot tell whether it is the original 2.4.41 or Debian's 2.4.41-4ubuntu3.15 with dozens of patches applied.
Why banner matching fails
Most vulnerability scanners match a detected version number against a CVE database. If the detected version is lower than the fixed version, they flag it. That logic works when the version number is honest. It fails when a distribution backports a fix because the version number never reaches the "fixed" upstream value even though the vulnerability is patched.
The result is a false positive. It is not a scanner bug, but it is a scanner limitation. Any tool that only looks at banners will produce these on Debian and Ubuntu systems.
How to triage it quickly
First, identify the package manager. If the target is Debian or Ubuntu, treat every CVE matched against a banner version as suspicious until proven otherwise. Look up the exact package version in the distribution's security tracker. Debian has security-tracker.debian.org; Ubuntu has ubuntu.com/security/CVE. Those pages list the fixed package version for each release.
Second, prefer authenticated checks when you can. If you have shell access, run the package manager: apt list --installed or dpkg -l will give you the real package version, including the distro-specific suffix. Compare that against the security tracker, not against the upstream CVE metadata.
What a scanner should do
A good scanner reports the evidence it has and does not overclaim. It should flag the detected banner version, note that the host may be running a backported version, and point you at the distribution security tracker. It should not present a banner match as a confirmed exploitable vulnerability.
The broader lesson
Version-based CVE matching is a starting point, not a verdict. The real signal is whether the vulnerability is actually present on this specific system. That means combining banner data with package-manager data, configuration context, and, when it matters, a proof-of-concept test. If you treat every CVE hit as a ticket, you will drown your team in false positives and train them to ignore the scanner. If you triage the backport cases first, you keep the noise low and the real issues visible.