Port 1023Reserved Port
Port 1023 is a reserved network port, historically set aside to prevent conflicts and ambiguities during network communications. It sits just below the commonly accepted range for dynamic or private ports, serving as a transitional boundary between well-known ports and ephemeral ports allocated by the operating system during client connections..
- transport
- tcp · udp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 5,099
2 transports registered
payload readable on path
registered with iana
caution
rank 912 of 993 · top 92%
Technical Details
what runs on :1023-
Port 1023 is the highest-numbered system or well-known port, as Internet Assigned Numbers Authority (IANA) has traditionally defined 0-1023 as system ports requiring privileged access. This reservation ensures separation from user-level or ephemeral ports (1024-65535), helping OSes and network devices handle connections more predictably.
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Historically, lower ports required administrative privileges to bind processes, safeguarding critical services like HTTP (80), SSH (22), and DNS (53). Port 1023, thus, marks the boundary preventing unprivileged processes from impersonating core services.
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Technically, 1023’s reserved status means it is not assigned a specific protocol or service and should not be used for custom application development or proprietary services. Leaving it unassigned helps maintain clarity and avoids overlapping assignments as protocols evolve.
Security Information
exposure of :1023risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
system averages 3.9 across 342 ports — this one sits 0.1 above.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
official
registered with iana for this service — scanners fingerprint it by number
reachable over
tcp · udp
udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite
security overview
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Common Vulnerabilities: Since port 1023 is reserved and unassigned, it generally does not host active services. However, some attackers may exploit misconfigurations, assigning insecure applications or backdoors to this port assuming low monitoring. Privilege escalation vulnerabilities can also arise if permission policies around system port usage are lax.
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Common Mitigations:
- Firewalls should explicitly monitor and restrict unexpected ingress/egress on port 1023.
- Avoid assigning custom services to this port, maintaining its reserved status.
- Implement strict privileged access controls to prevent unprivileged processes from binding to reserved ports.
- Conduct periodic scans to detect unauthorized listening services or suspicious activity involving port 1023.
Related Ports
the 8 most looked-up other ports in system — 342 ports carry that label.
| port | service | risk | |||
|---|---|---|---|---|---|
| :8888 | Sun Answerbook & Alt HTTP | TCP | Web Services | caution | 123.9k |
| :4664 | Google Desktop Search | TCP | System | caution | 67.2k |
| :8008 | IBM HTTP Server Admin | TCP | Web Services | caution | 58.3k |
| :3268 | Microsoft Global Catalog (GC) | TCPUDP | Security | caution | 54.6k |
| :135 | Microsoft EPMAP | TCPUDP | Security | caution | 51.9k |
| :9080 | WebSphere HTTP Transport (default) | TCP | Web Services | caution | 51.6k |
| :23 | Telnet | TCP | Remote Access | caution | 34.8k |
| :12489 | NSClient Monitoring Agent | TCP | Network Services | caution | 30.0k |
risk mix of the 8 listed
- caution100%
0 of 8 encrypted