This is similar to an earlier bug https://issues.jenkins-ci.org/browse/JENKINS-24402?jql=text%20~%20%22jsch%22

Same problem has resurfaced in the later releases of JSch, because of that we get failed builds intermittently with the below error.

JSch has included a fix for this problem in the latest version , v0.1.55.

Upgrading Jenkins SSH plugin to this version should fix this problem.

These discussion forums provide the context

discussion about the issues in JSch and fix https://sourceforge.net/p/jsch/bugs/111/

discussion about previous fix in Jenkins SSH plugin and further recurrences https://stackoverflow.com/questions/12279836/ssh-using-jschexception-verify-false-sometimes-fails

Stacktrace:

[SSH] executing...
[SSH] Exception:Session.connect: java.security.SignatureException: Invalid encoding for signature
com.jcraft.jsch.JSchException: Session.connect: java.security.SignatureException: Invalid encoding for signature
at com.jcraft.jsch.Session.connect(Session.java:565)
at org.jvnet.hudson.plugins.CredentialsSSHSite.createSession(CredentialsSSHSite.java:132)
at org.jvnet.hudson.plugins.CredentialsSSHSite.executeCommand(CredentialsSSHSite.java:208)
at org.jvnet.hudson.plugins.SSHBuilder.perform(SSHBuilder.java:104)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:744)
at hudson.model.Build$BuildExecution.build(Build.java:206)
at hudson.model.Build$BuildExecution.doRun(Build.java:163)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:504)
at hudson.model.Run.execute(Run.java:1798)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:97)
at hudson.model.Executor.run(Executor.java:429)