Upgrade jenkins plugins via random SSH Port. You have to enable random SSHD port in Jenkins security settings.

gistfile1.txt

#!/bin/bash
JENKINS_HOST=jenkins_host
BASE_URL=http://${JENKINS_HOST}/jenkins/
SSH_ENDPOINT=$(curl -Lv ${BASE_URL}login 2>&1 | grep 'X-SSH-Endpoint')
USER=$(whoami)
echo "${SSH_ENDPOINT}"
PORT=$(echo "${SSH_ENDPOINT}" | awk -F: '{printf("%d", $3);}' | tr -d "\n")
echo "port=${PORT}"
echo "user=${USER}"
echo "host=${JENKINS_HOST}"

# ssh -l ${USER} -p ${PORT} ${JENKINS_HOST} help
UPDATE_LIST=$(ssh -l ${USER} -p ${PORT} ${JENKINS_HOST} list-plugins | grep -e ')$' | awk '{ print $1 }')
if [ ! -z "${UPDATE_LIST}" ]; then 
    echo Updating Jenkins Plugins: ${UPDATE_LIST}; 
    ssh -l ${USER} -p ${PORT} ${JENKINS_HOST} install-plugin ${UPDATE_LIST};
    ssh -l ${USER} -p ${PORT} ${JENKINS_HOST} safe-restart;
fi

exit 0