[ Reason ]
This fixes CVE-2026-19566, a minor input sanitizing fix.  It's a
followup to CVE-2026-49942, which was not complete.

[ Impact ]
Depending on the usage of the library this may be a security issue.

[ Tests ]
salsa-ci passed execpt test-uscan (which isn't a problem for a
trixie-pu).  See
https://salsa.debian.org/perl-team/modules/packages/libnet-cidr-set-perl/-/pipelines/1177382
The patches ships its own test cases, which succeed.

[ Risks ]
Hopefully none...

[ Checklist ]
  [x] *all* changes are documented in the d/changelog
  [x] I reviewed all changes and I approve them
  [x] attach debdiff against the package in stable
  [x] the issue is verified as fixed in unstable

[ Changes ]
Minimal fix for CVE-2026-19566 including a new test case.

[ Other info ]
According to
https://security-tracker.debian.org/tracker/CVE-2026-19566 this is a
minor issue, so it's not for DSA but for a point release.

Greetings
Roland