Looking at the change it seems like log4j was removed as a dependency - but is still being used by the code? Though not sure how it's even compiling so maybe something completely unrelated is going on.

Jenkins Version 2.414.3

Upgrading from 2.0.65.vd26b_5b_9b_de4d to 2.0.68.va_d21a_12a_6476 caused a crash when using sshPut. Downgrade of only this plugin completely fixed issue.

{{
Also: org.jenkinsci.plugins.workflow.actions.ErrorAction$ErrorId: 57495606-8948-4a9b-8f5e-1e7bf231a4b3
java.lang.NoSuchMethodError: 'void org.apache.log4j.MDC.put(java.lang.String, java.lang.String)'
at org.jenkinsci.plugins.sshsteps.util.SSHStepExecution.lambda$start$0(SSHStepExecution.java:81)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
Finished: FAILURE
}}

Line: https://github.com/jenkinsci/ssh-steps-plugin/blob/50fdfda7a4476409a6d3adcf56d260522ab0c799/src/main/java/org/jenkinsci/plugins/sshsteps/util/SSHStepExecution.java#L81

Diff: https://github.com/jenkinsci/ssh-steps-plugin/compare/2.0.65.vd26b_5b_9b_de4d...2.0.68.va_d21a_12a_6476