I’m not very familiar with jar files but they’re just zip files, right?
Short of a known way to reproduce this error from scratch in a fresh installation of Jenkins, the diagnostic path I would start with is opening the Groovy console on an affected agent and running
You would expect to see something like
Result: [https://jenkins/jnlpJars/remoting.jar, https://host:jenkins/jnlpJars/remoting.jar]
If you see something else, then we have a lead. If you see the above, then some other diagnostics would be needed.
Configuration worked before and did not change, so it's definitely related to the update
“Related” to the update perhaps, but that does not imply a bug in any software which was updated. Incidental changes in behavior often cause existing misconfigurations to become manifest. Similarly, my proposed rewrite in
JENKINS-48344 would delete the code path which evidently triggers this problem, but that does not make it a “fix” for this issue.