Port 631CUPS
The Common Unix Printing System (CUPS) is a modular printing system for Unix-like operating systems. It allows a computer to act as a print server, managing print jobs and queues and providing network printing capabilities across diverse platforms and devices..
- transport
- tcp · udp
- in transit
- cleartext
- assignment
- unofficial
- risk
- 4/10
- lookups
- 9,315
2 transports registered
payload readable on path
used by convention
caution
rank 515 of 993 · top 52%
1 other service is registered on port 631. compare all 2 →
Technical Details
what runs on :631Overview
The Common Unix Printing System (CUPS) is an open-source printing system that acts as a print spooler and scheduler. It utilizes the Internet Printing Protocol (IPP) for managing print jobs and queues, making it easier to share printers across networks. CUPS supports various printer drivers and works across multiple Unix-like systems, including Linux and macOS.
Protocols and Communication
CUPS communicates primarily over port 631 using IPP, which is based on HTTP. This allows clients to submit print jobs, query print status, and manage printer capabilities from remote systems. The service supports both TCP and UDP transport protocols, although TCP is more frequently used for reliable transmission. CUPS can also interface with legacy protocols such as LPD and SMB.
System Integration
Designed to be highly modular, CUPS uses filters and backends to communicate with different printer models and types. It offers a web-based management interface accessible via the same port, providing administrators an easy way to add, configure, and monitor printers and print jobs. Its compatibility with IPP Everywhere also facilitates driverless printing on modern devices.
Security Information
exposure of :631risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
network services averages 3.9 across 604 ports — this one sits 0.1 above.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
unofficial
used by convention, not registered — what answers here varies by deployment
reachable over
tcp · udp
udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite
security overview
Common Vulnerabilities
- Unauthenticated Access: Misconfigured CUPS servers may allow unauthenticated users to submit or manage print jobs.
- Information Disclosure: Due to verbose HTTP error messages or directory listings.
- Remote Code Execution: Exploitable buffer overflows or vulnerabilities in filter backends have historically led to arbitrary code execution.
- Network Exposure: Exposure on public interfaces can allow attackers to enumerate printers or exploit known flaws.
Common Mitigations
- Access Controls: Restrict access to port 631 using firewalls and CUPS configuration directives.
- Authentication: Enable strong authentication mechanisms for administration and printing tasks.
- Patch Management: Regularly update CUPS to mitigate known vulnerabilities.
- Network Segmentation: Limit network exposure to trusted internal segments.
- Disable Unused Protocols: If UDP or other protocols aren't needed, disable them to reduce attack surface.
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risk mix of the 8 listed
- caution100%
0 of 8 encrypted