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// File transfer & sharing

Port 20048: NFS mount protocol

Port 20048 is assigned by IANA to mountd (NFS mount protocol).

20048

How mountd works

File transfer & sharing
client:200481/32/33/3mountd client:200481/32/33/3mountd

Files are sent over port 20048 in pieces and reassembled on the other side.

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
File transfer & sharing
01 Security

Is port 20048 dangerous?

We have no specific security note for port 20048. Its risk depends on the program actually listening on it. General advice for file transfer & sharing services:

  • Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).
  • Disable anonymous access and restrict shares or exports to known hosts.
  • Never publish file sharing protocols to the Internet.
02 Registry

IANA registry entries for port 20048

ServicePortTransportDescriptionReferenceUpdated
mountd 20048 TCP, UDP NFS mount protocol - 2010-08-09

// source: IANA service name and port number registry

03 Check it

Which program uses port 20048, and is it reachable?

Linux

sudo ss -ltnup 'sport = :20048'      # process listening on 20048
sudo lsof -nP -i :20048

macOS

sudo lsof -nP -i :20048

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 20048 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 20048
netstat -ano | findstr :20048

From another machine

nmap -p 20048 -sV <host>
sudo nmap -sU -p 20048 <host>
nc -zv <host> 20048

Block it in the firewall

sudo ufw deny 20048/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 20048" -Direction Inbound -LocalPort 20048 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 20048 used for?

Port 20048 is assigned by IANA to mountd (NFS mount protocol).

Is port 20048 TCP or UDP?

Port 20048 is registered for TCP and UDP.

Is it safe to open port 20048?

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. Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).

How do I check if port 20048 is open?

On Linux run "ss -ltnup 'sport = :20048'", on macOS "lsof -nP -i :20048", and on Windows "netstat -ano | findstr :20048" to see the local process. From another machine, "nmap -p 20048 <host>" shows whether it is reachable.

05 Related
:445 SMB tcp · udp · critical risk :21 FTP tcp · udp · sctp · high risk :139 NetBIOS Session tcp · udp · high risk :69 TFTP udp · tcp · high risk :2049 NFS tcp · udp · sctp · high risk :873 rsync tcp · udp · high risk :20 File Transfer [Default Data] tcp · udp · sctp :115 Simple File Transfer Protocol tcp · udp

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