SuSE: nkitb/nkitserv/telnetd vulnerabiilties
Summary
______________________________________________________________________________
SuSE Security Announcement
Package: nkitb/nkitserv/telnetd
Announcement-ID: SuSE-SA:2001:029
Date: Mon Sep 3 12:55:58 MEST 2001
Affected SuSE versions: [6.1, 6.2,] 6.3, 6.4, 7.0, 7.1, 7.2
Vulnerability Type: remote code execution
Severity (1-10): 8
SuSE default package: yes
Other affected systems: All UN*X Systems shipping BSD derived telnetd
Content of this advisory:
1) security vulnerability resolved: Buffer overflow in in.telnetd
problem description, discussion, solution and upgrade information
2) pending vulnerabilities, solutions, workarounds
3) standard appendix (further information)
______________________________________________________________________________
1) problem description, brief discussion, solution, upgrade information
The telnet server which is shipped with SuSE distributions contains a
remotely exploitable buffer-overflow within its telnet option
negotiation code.
This bug is wide-spread on UN*X systems and affects almost
all implementations of telnet daemons available.
SuSE 7.2 distribution ships the telnet-server package which
contains the vulnerable telnet daemon. This package has been fixed.
The SuSE Linux distributions 6.3 and 6.4 contain versions and
implementations of the telnet-daemon that are vulnerable, but the
complexity of the code requires a full source code audit of the
software. In order not to further delay the release of the packages
for the SuSE Linux 7.x distributions, we recommend to disable the
telnet daemon on the 6.x distributions. This can be done by
commenting out the line in /etc/inetd.conf that starts with
"telnet", and then reloading the inetd configuration using the
command "killall -1 inetd". Another option is to not start the inetd
in the first place if you do not need any of the services provided
by the inetd daemon. Disabling inetd permanently involves killing
the running inetd process ("killall -TERM inetd") and setting the
variable START_INETD in /etc/rc.config to "no" (as opposed to
"yes").
Disabling the telnet service is the preliminary solution/workaround
against the problems with the telnetd daemon. We hope to be able to
provide a better solution.
The SuSE Linux distributions 7.0, 7.1 and 7.2 have similar
implementations of in.telnetd, and for all of these distributions
there are update packages available. Please note that the package
that contains the /usr/sbin/in.telnetd program (the server
program) has changed over the different releases of the SuSE Linux
distribution. In the 7.0 and 7.1 distributions the package is called
"nkitserv". The 7.2 distribution lists the telnet server in the
package "telnet-server".
Please download the packages and verify them as described in section 3.
After successfull authentication you can update your packages with
the command `rpm -Uhv file.rpm'.
Further action should not be necessary to activate the update since
the in.telnetd daemon is started from a new by inetd upon every
accepted connection from the network.
Regardless of the availiability of fixed packages of the
telnet-daemon, SuSE Security strongly recommend to disable the
telnet service if you do not use it. In addition to that, only
cryptographically protected protocols such as secure shell (ssh,
package openssh) can be an efficient countermeasure against sniffing
and spoofing type attacks. Due to significantly more comfort (such
as X11-forwarding, multiple authentication methods, ...), the
transition to ssh should be worth the effort in any case.
i386 Intel Platform:
SuSE-7.2
0adc05af9762bd4c63eee464ca3131d1
source rpm:
fe313553d1a6f022c7eb2f87ccd6772f
SuSE-7.1
e0636eec04ccf2129b0e2ea0ee40c231
source rpm:
57760fcd8e064e89591203f7ba9adefc
SuSE-7.0
e8a859d5a648a572fc08628247c1e2d6
source rpm:
33d4abc52926ac957f21b8c8aae7adce
Sparc Platform:
SuSE-7.1
3ef64d1cae35be51c9eff9bebcf4cf79
source rpm:
4cb76a16bd2f53c37a7cee728ea21c81
SuSE-7.0
f4901a4a271657d0379aff114d30b912
source rpm:
ad909d8e3d2d0a617a5a9f6e3d7cd74d
AXP Alpha Platform:
SuSE-7.1
efad3412a8d333947bcf74695c023ea8
source rpm:
94d0dba0396e41b4afbd3ef61c4fd8aa
SuSE-7.0
934525486e72a5cc98736f4cb1217f93
source rpm:
a6623ff6d9439dea40f24ff35acefe99
Power PC Platform:
SuSE-7.1
4da51d1a38095e81ee389094b0f21160
source rpm:
499b282f614835fe7a7b1a9ab039c56d
SuSE-7.0
262f3fc3653042976c8cc36a2cd7e44d
source rpm:
7cba8393bb8a71cf4d39fb480a71b42e
______________________________________________________________________________
2) Pending vulnerabilities in SuSE Distributions and Workarounds:
- w3m
The w3m browser contains a buffer-overflow which allows remote-attackers to execute arbitrary code or to crash the w3m web-client when viewing
special crafted sites. Please update to the newest w3m packages available
on the ftp-server.
- dip
The dip program is executable as setuid root program for users in the
"dialout" group, a privilege that has been issued by the administrator for
a trusted user group. This bug will be corrected in future releases of the
SuSE Linux distribution.
______________________________________________________________________________
3) standard appendix: authenticity verification, additional information
- Package authenticity verification:
SuSE update packages are available on many mirror ftp servers all over
the world. While this service is being considered valuable and important
to the free and open source software community, many users wish to be
sure about the origin of the package and its content before installing
the package. There are two verification methods that can be used
independently from each other to prove the authenticity of a downloaded
file or rpm package:
1) md5sums as provided in the (cryptographically signed) announcement.
2) using the internal gpg signatures of the rpm package.
1) execute the command
md5sum
References
