Let's suppose I have a project called myLib-1.1.0. This project has a dependency on lib-dependency-1.2.3.
If there's a new version for this dependency and I need to use it, should I change my project version as well? No other modifications are made to myLib.
At the same time myLib is a dependency for various other projects. My main concern is the impact of a small change in a dependency might have upstream.
Yes. In maven, released versions are immutable. If you release 1.1.0 with a dependency to lib-dependency-1.2.3 then that's it.
If you change to depend on lib-dependency-1.2.4 then that's a new version. You should not redeploy 1.1.0 since some people might have already pulled that (supposedly immutable) 1.1.0. So that means you need a different version, even if it's a just a new qualifier (myLib-1.1.0-RC-2 for example, but better just 1.1.1)
Maven doesn't recheck remote repos for release versions once it has it in the local repo, so if someone has 1.1.0 already locally, they will not get the new, fixed 1.1.0.
And about your rippling problem. Upstream projects should depend on the lowest acceptable released version. i.e. if the upstream project itself is ok with myLib-1.1.0 because it doesn't need (indirectly) lib-dependency-1.2.4 then it should stay with 1.1.0
Any code change that potentially affects the behavior should be given a new version number, in other words: anything that's not an absolute trivial change should be given a new version number. A changed dependency would definitely qualify for that because, unless you do a thorough code inspection of the dependency, you have no reason to assume that they only made absolute trivial changes.
Changes are often advertised as "small" (similar to being absolutely trivial as I call it above), but they hardly ever are. They may be negligible in someone's use case, but not in someone else's use case. I've even seen circumstances where there were only changes to Javadocs in a project that would break things down the line. (You could argue about how smart it is for someone to depend that strongly on Javadoc, but that's besides the point, isn't it?)
That is not to say that you can't accumulate changes and release a bunch of them as a single release. While accumulating, your project is in flux, and should have a ...-SNAPSHOT version. There should be no two versions of myLib-1.1.0 (without the -SNAPSHOT) that have even the least little change.
The fact that you're re-releasing your project also makes explicit the fact that regression testing and such should be redone to validate that it's still working with the changes in its dependency.
