An Nmap version scan reveals the web server version for pcsd in a Pacemaker cluster

Issue

• The Server header is empty in pcsd's HTTP responses, but a port scan still reveals the web server version.

nmap -sV --script http-headers -p 2224 xxx.xxx.xxx.xxx
Starting Nmap 7.91 ( https://nmap.org ) at 2020-11-25 16:34 HKT
Nmap scan report for xxx.xxx.xxx.xxx
Host is up (0.00029s latency).

PORT     STATE SERVICE  VERSION
2224/tcp open  ssl/http WEBrick httpd 1.3.1 (Ruby 2.0.0 (2015-12-16); OpenSSL 1.0.2k)
| http-headers:
|   Content-Type: text/html;charset=utf-8
|   Content-Length: 49864
|   Server:
|   Strict-Transport-Security: max-age=604800
|   X-Xss-Protection: 1; mode=block
|   X-Content-Type-Options: nosniff
|   X-Frame-Options: SAMEORIGIN
|   Date: Wed, 25 Nov 2020 08:34:52 GMT
|   Connection: close
|
|_  (Request type: HEAD)
|_http-server-header: <empty>

• A port scanner reveals the OpenSSL version on the pcsd port (2224/tcp by default).