Writedump in CF2025

To me, the situation you describe suggests 2 things:

1.  There is a difference, perhaps a subtle one, between your 2023 and 2025 environments. For example, does the 2025 environment have a faulty Application.cfc or no Application.cfc at all?  
2.  The error is unlikely to have been caused by the writedump code. It is most likely caused by an abort or by a failed abort in an internal ColdFusion function or tag. To see what is causing the issue, use try/catch:
   

   try {
       /*** The code causing the issue ***/
   }
   catch (any exception) {
       writedump(exception);
   }​

@SaschaD , first it may surprise you to hear but I don't get that error, on any machine running CF2025, whether update 2 or 1 or 0, and as tested on multiple machines running both Windows and Linux. 

If you may want to see it for yourself, run the code on either or both of the sites, cffiddle.org or trycf.com, which let you choose what CF version to run on. That's a helpful tip for when anyone wants to test such things on a machine other then their own.

And here's some code that anyone could try, which reports also the CF version, update level, and OS:

<cfscript>
writedump(var=server.coldfusion,abort=true)
</cfscript>

Let us know what you may find.

As for the error you get, if it proves to be unique to your own machine, one thing to consider is whether your application of any update to CF2025 may have had an error. It can happen. See the update log found in cf's cfusion/hf-updates folder, in the folder under that for the latest update you applied, then within that folder see the longest-named log file, which includes the date/time you ran the update. Then look at about line 70, to see a table tracking the count of successes, warning, fatalerrors, and nonfatalerrors. Are the latter two non-zero? If so, try re-running the update. (I also have a blog post with more on dealing with CF update problems.)