Would like to request nagios plugins updated to >= 2.4.1 from 2.3.5, to fix a few issues.
As was already mentioned in comments, Ubuntu distrubutes its packages under a policy where they "freeze" most packages at their versions (with a few exceptions like browsers) and manually backport fixes from the newer versions (so in the "version" string only the patch-release gets incremented). This sometimes even leads to funny situations, where a package may be identical to more recent "minor" release, but the version string is still at older one.
So what you can do is you can create report on Ubuntu launchpad for the package in question, where you'd mention the issues you encounter and the commit id that fixes the issues (or if you don't know the commit id, then at least just say it's fixed in newer version and let maintainers to figure it out). Maintainers should backport the fixes in question, so your package will be fixed without the version increment.
P.S.: I wouldn't hold high hopes it will work though. I mean, the process I described is robust, but in my experience of Launchpad interaction, the reports frequently get lost. Even for packages with many subscribers and having a fix in the report. I'm not sure why that happens, but it's something Ubuntu/Canonical-specific. In Archlinux or Fedora, in my experience, reports are almost always acted upon (I'm saying "almost" just to cover the fact that nothing can be perfect, but TBH I haven't seen reports with no reply).