- Serve it over HTTPS only and check the HTTP security headers.
- Keep admin consoles and development servers off the Internet.
- Patch the application server and remove default credentials and sample apps.
Port 8991: webmail HTTPS service
Port 8991 is assigned by IANA to https-wmap (webmail HTTPS service).
8991
How https-wmap works
WebA browser sends an HTTP request to port 8991 and the https-wmap server sends the page back.
- Transport
- TCP · UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- Web
Is port 8991 dangerous?
We have no specific security note for port 8991. Its risk depends on the program actually listening on it. General advice for web services:
IANA registry entries for port 8991
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| https-wmap | 8991 | TCP, UDP | webmail HTTPS service | - | 2007-12-03 |
// source: IANA service name and port number registry
Which program uses port 8991, and is it reachable?
Linux
sudo ss -ltnup 'sport = :8991' # process listening on 8991
sudo lsof -nP -i :8991macOS
sudo lsof -nP -i :8991
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 8991 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 8991 netstat -ano | findstr :8991
From another machine
nmap -p 8991 -sV <host> sudo nmap -sU -p 8991 <host> nc -zv <host> 8991
Block it in the firewall
sudo ufw deny 8991/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 8991" -Direction Inbound -LocalPort 8991 -Protocol TCP -Action Block # Windows
What is port 8991 used for?
Port 8991 is assigned by IANA to https-wmap (webmail HTTPS service).
Is port 8991 TCP or UDP?
Port 8991 is registered for TCP and UDP.
Is it safe to open port 8991?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Serve it over HTTPS only and check the HTTP security headers.
How do I check if port 8991 is open?
On Linux run "ss -ltnup 'sport = :8991'", on macOS "lsof -nP -i :8991", and on Windows "netstat -ano | findstr :8991" to see the local process. From another machine, "nmap -p 8991 <host>" shows whether it is reachable.
Other web ports
:443 HTTPS tcp · udp · sctp · low risk :80 HTTP tcp · udp · sctp · moderate risk :8080 HTTP alternate tcp · udp · high risk :8443 HTTPS alternate tcp · udp · moderate risk :3000 Dev servers / Grafana tcp · udp · moderate risk :5000 Flask / Docker registry / UPnP tcp · udp · moderate risk :8000 HTTP alternate (dev) tcp · udp · moderate risk :8888 Jupyter / HTTP alternate tcp · udp · high risk