High
utility.c in telnetd in netkit telnet through 0.17 allows remote attackers to execute arbitrary code via short writes or urgent data, because of a buffer overflow involving the netclear and nextitem functions.
Execution of arbitrary code
Cisco
Cisco IOS XE Software
Refer to vendor advisory for the list of affected products and upgraded patches.
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-telnetd-EFJrEzPx