Some Jenkins users cannot login into the instance and the container is blowing the stacktrace below right after the login issue.
java.lang.IllegalStateException: JBWEB002005: Header count exceeded allowed maximum 
- CloudBees Jenkins Platform
- JBoss container
This issue is likely happening because this user is a member of a long tree of groups. This snippet shows you the most probable reason why JBoss is showing that stacktrace.
To correctly determinate the root cause of the issue you will need to generate a HAR so the headers populated by Jenkins could be checked.
To workaround this problem you could increase the value of
MAX_COUNT by using the system property
<system-properties> <property name="org.apache.tomcat.util.http.MimeHeaders.MAX_COUNT" value="512"/> </system-properties>