Port 5031AVM CAPI-over-TCP
AVM CAPI-over-TCP enables ISDN signaling data to be transmitted over Ethernet networks, effectively encapsulating ISDN protocols within TCP/IP for remote access or integration. This facilitates the bridging of traditional ISDN communication with modern IP infrastructure, often serving AVM's Fritz!Box devices and similar hardware..
- transport
- tcp · udp
- in transit
- cleartext
- assignment
- unofficial
- risk
- 4/10
- lookups
- 11,959
2 transports registered
payload readable on path
used by convention
caution
rank 331 of 993 · top 33%
Technical Details
what runs on :5031AVM CAPI-over-TCP facilitates the tunneling of ISDN signaling data across IP-based networks. It encapsulates the CAPI (Common ISDN Application Programming Interface) commands and responses within TCP or UDP packets, enabling ISDN services to function over Ethernet rather than physical ISDN lines. This is especially beneficial in environments where legacy ISDN devices need integration with IP infrastructures.
The protocol is commonly used by AVM devices such as Fritz!Box routers, providing an interface for telephony services across the network. By carrying CAPI messages over TCP/IP, the system can maintain compatibility with ISDN software and applications even if native ISDN hardware is unavailable onsite.
Operationally, this tunnel allows remote access to ISDN lines or virtualized ISDN services. It can be utilized for call signaling, D-channel messaging, and facsimile data, maintaining the full feature set of traditional ISDN over an Ethernet transport.
Security Information
exposure of :5031risk 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 associated with AVM CAPI-over-TCP include:
- Lack of transport encryption, making ISDN signaling data susceptible to eavesdropping.
- Potential exposure to denial-of-service if authentication or access controls are insufficient.
- Unauthorized access leading to misuse of telephony services or toll fraud.
Mitigations include:
- Deploying encrypted tunnels like VPNs to secure signaling data in transit.
- Implementing strict network-based access controls and limiting the IP ranges allowed to connect.
- Updating devices and software to patch known vulnerabilities.
- Enabling authentication and logging to detect suspicious activities.
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risk mix of the 8 listed
- caution100%
0 of 8 encrypted