Telnet accepted for switch management
At a glance
Base severity
Area
Platform
Evidence level
Benchmark reference
Reads the export, not the device
ConfigProof reads a configuration export. This control is evaluated against the objects in that file, and it reports what the file says. It does not connect to the device and sees no traffic, so a finding here describes the configuration, not what the firewall is doing right now.
Why it matters
Anyone able to observe the management path can read the password of every administrator who logs in over Telnet and take over the switch.
How to fix it
Web interface
The steps below are written for the web interface. A finding raised on your own export carries the same steps with your object names filled in.
- Allow only SSH on every VTY line: line vty 0 15, transport input ssh.
- On NX-OS: no feature telnet.
Command line
Cisco IOS-XE CLI
configure terminalline <line>transport input sshendwrite memory
An example. Values in angle brackets are yours to supply; a finding on your own export fills in the names it read. Typed in configuration mode; copy running-config startup-config saves it, with no separate commit. Read every line first.
Read it back
show running-config | section line vtyshow ip ssh
Values to fill in1
- <line>
- The line to restrict, for example vty 0 4
Before you type it3
- Written from the Cisco IOS-XE 17 and NX-OS 9 and 10 command references and not run on a device: read each line before you paste it.
- Confirm your own session is not using the service you are turning off.
- On a Nexus (NX-OS) switch, Telnet is a feature: no feature telnet.
How to confirm the fix
- show running-config | section line vty shows transport input ssh on every VTY line.
- On NX-OS, show feature | include telnet shows telnet disabled.
Limits
- A VTY line whose transport is not written follows the release's default, which varies; such lines are counted as not read rather than judged.
Compliance references
CIS Cisco IOS 17.x Benchmark v2.0.0
Covers part of the recommendation
Where a control aligns with a recommendation of the CIS Cisco IOS 17.x Benchmark v2.0.0, that recommendation is cited as a reference. Only that version was checked. A reference is not a certification.
More in Administrators and Access
- SW-MGT-002Management lines open to any source address
- SW-MGT-003Management session timeout disabled or long
- SW-MGT-004SSH version 1 not refused
- SW-MGT-005Plain HTTP management enabled
- SW-MGT-006Enable password stored in clear text or reversible form
- SW-MGT-007Password hashed with MD5 (type 5)
- SW-MGT-008Local account password stored in clear text or reversible form
- SW-MGT-011No login banner
See it on your own firewall
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