Multiple Telnet clients contain a data length validation flaw which may allow a server to induce arbitrary code execution on the client host.
The Telnet network protocol is described in RFC854 and RFC855 as a general, bi-directional communications facility. The Telnet protocol is commonly used for command line login sessions between Internet hosts.
Many Telnet client implementations may be vulnerable to a flaw which may allow arbitrary code to be executed on the connected client. The Telnet server may supply a specially crafted reply containing a larger number of RFC1184 LINEMODE "Set Local Character" (SLC) suboption commands, which are not checked for proper length before being stored into a fixed length buffer. Affected Telnet clients possibly include the BSD Telnet implementation and the MIT Kerberos distribution.
A remote server may be able to execute arbitrary code under the permissions of the user running the Telnet client on the local host.
Apply an update from your vendor
As a workaround, the client may explicitly disable the LINEMODE mode before connecting in order to prevent LINEMODE command processing. In addition, as a best practice clients should never connect to unknown servers.
Apple Computer, Inc.
F5 Networks, Inc.
MiT Kerberos Development Team
Red Hat, Inc.
Sun Microsystems, Inc.
Ingrian Networks, Inc.
Juniper Networks, Inc.
MontaVista Software, Inc.
Sequent Computer Systems, Inc.
The SCO Group (SCO Linux)
The SCO Group (SCO Unix)
Wind River Systems, Inc.
Thanks to iDEFENSE Labs for reporting this vulnerability.
This document was written by Ken MacInnis.
|Date First Published:||2005-03-29|
|Date Last Updated:||2005-12-22 21:22 UTC|