I am trying to upgrade to a newer version of aspectjrt than the one that comes with Eclipse. I updated the version number in maven pom.xml. Eclipse doesn't seem to pick it up, it still displays the built-in version on its classpath.
Which version of the library does m2eclipse uses?
When you add AspectJ nature to your Eclipse project, then you by default also get the AspectJ plugin's aspectjrt.jar file on the project's build path.
Remove this and let the Maven pom file reference to the preferred version.
You can remove the AspectJ Runtime Library with selecting it --> right-click --> build path --> remove.
It can be found together with your other libraries below the source folders or from the project's Java Build Path menu.