telnetd in GNU Inetutils through 2.3, MIT krb5-appl through 1.0.3, and derivative works has a NULL pointer dereference via 0xff 0xf7 or 0xff 0xf8. In a typical installation, the telnetd application would crash but the telnet service would remain available through inetd. However, if the telnetd application has many crashes within a short time interval, the telnet service would become unavailable after inetd logs a "telnet/tcp server failing (looping), service terminated" error. NOTE: MIT krb5-appl is not supported upstream but is shipped by a few Linux distributions. The affected code was removed from the supported MIT Kerberos 5 (aka krb5) product many years ago, at version 1.8.

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.

Buffer overflow in the handle_packet function in mactelnet.c in the client in MAC-Telnet 0.4.3 and earlier allows remote TELNET servers to execute arbitrary code via a long string in an MT_CPTYPE_PASSSALT control packet.

telnetd.exe in Pragma TelnetServer 7.0.4.589 allows remote attackers to cause a denial of service (process crash and resource exhaustion) via a crafted TELOPT PRAGMA LOGON telnet option, which triggers a NULL pointer dereference.

SLnet.exe in SeattleLab SLNet RF Telnet Server 4.1.1.3758 and earlier allows user-assisted remote attackers to cause a denial of service (crash) via unspecified telnet options, which triggers a NULL pointer dereference. NOTE: the crash is not user-assisted when the server is running in debug mode.

Sorin Chitu Telnet-FTP Server 1.0 allows remote authenticated users to cause a denial of service (crash) via consecutive RETR commands. NOTE: The provenance of this information is unknown; the details are obtained solely from third party information.

Directory traversal vulnerability in Sorin Chitu Telnet-FTP Server 1.0 allows remote authenticated users to list contents of arbitrary directories and download arbitrary files via a .. (dot dot) sequence in an FTP command argument, as demonstrated by RETR (GET) or STOR (PUT). NOTE: The provenance of this information is unknown; the details are obtained solely from third party information.

Multiple unspecified vulnerabilities in multiple FITELnet products, including FITELnet-F40, F80, F100, F120, F1000, and E20/E30, allow remote attackers to cause a denial of service via crafted DNS messages that trigger errors in (1) ProxyDNS or (2) PKI-Resolver, as demonstrated by the OUSPG PROTOS DNS test suite.

Multiple buffer overflows in the getterminaltype function in telnetd for Heimdal before 0.6.5 may allow remote attackers to execute arbitrary code, a different vulnerability than CVE-2005-0468 and CVE-2005-0469.

Certain BSD-based Telnet clients, including those used on Solaris and SuSE Linux, allow remote malicious Telnet servers to read sensitive environment variables via the NEW-ENVIRON option with a SEND ENV_USERVAR command.