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Technical Cyber Security Alert 2007-59A

Technical Cyber Security Alert 2007-59A
Posted Mar 6, 2007
Authored by US-CERT | Site us-cert.gov

Technical Cyber Security Alert TA07-059A - A worm is exploiting a vulnerability in the telnet daemon (in.telnetd) on unpatched Sun Solaris systems. The vulnerability allows the worm (or any attacker) to log in via telnet (23/tcp) with elevated privileges.

tags | advisory, worm, tcp
systems | solaris
advisories | CVE-2007-0882
MD5 | 3c73f4b71f6456ca1c51dfdb2699536c

Technical Cyber Security Alert 2007-59A

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National Cyber Alert System

Technical Cyber Security Alert TA07-059A


Sun Solaris Telnet Worm

Original release date: February 28, 2007
Last revised: --
Source: US-CERT


Systems Affected

* Sun Solaris 10 (SunOS 5.10)
* Sun "Nevada" (SunOS 5.11)

Both SPARC and Intel (x86) architectures are affected.


Overview

A worm is exploiting a vulnerability (VU#881872) in the Sun Solaris
telnet daemon (in.telnetd).


I. Description

A worm is exploiting a vulnerability in the telnet daemon
(in.telnetd) on unpatched Sun Solaris systems. The vulnerability
allows the worm (or any attacker) to log in via telnet (23/tcp)
with elevated privileges. Further details about the vulnerability
are available in Vulnerability Note VU#881872 (CVE-2007-0882).

Because VU#881872 is trivial to exploit and sufficient technical
detail is publicly available, any attacker, not just this worm,
could exploit vulnerable systems.

Characteristics of the worm include, but are not limited to:

* Exploiting VU#881872 to log in via telnet as the users adm or lp
* Changing permissions on /var/adm/wtmpx to -rw-r--rw-
* Creating the directory .adm in /var/adm/sa/
* Adding .profile files to /var/adm/ and /var/spool/lp/
* Installing an authenticated backdoor shell on port 32982/tcp
* Modifying crontab entries for the users adm and lp
* Scanning for other hosts running telnet (23/tcp)

Sun has published information about the worm in the Security Sun
Alert Feed including an inoculation script that disables the telnet
daemon and reverses known changes made by the worm.


II. Impact

VU#881872 allows remote attacker to log on to a vulnerable system
via telnet and gain elevated privileges. The worm exploits this
vulnerability to compromise systems as described above. Since the
worm installs a backdoor shell, it is possible for an attacker with
knowledge of the authentication tokens to access a compromised
system and take any action with the privileges of the backdoor
shell process, likely adm or lp.


III. Solution

Apply a patch

To address VU#881872, apply the appropriate patches referenced in
Sun Alert Notification 102802.

Run inoculation script

To recover compromised systems, Sun has provided an inoculation script
that disables the telnet daemon and reverses known changes made by the
worm.

Note that the inoculation script only recovers from this particular
worm. Running the inoculation script does not guarantee system
integrity. A vulnerable system may be compromised in different ways
by attackers exploiting VU#881872 or using the backdoor installed
by the worm. To fully recover, it may be necessary to rebuild a
compromised system using trusted software sources. For more
information, see Recovering from an Incident.


IV. Workarounds

Until the appropriate patches can be applied, consider the
following workarounds.

Disable telnet

Telnet can be disabled by issuing the following command as root:

# /usr/sbin/svcadm disable telnet

Restrict telnet access

Restrict access to telnet (23/tcp) from untrusted networks such as
the Internet.

Use SSH instead of telnet

SSH provides a comparatively more secure method for remotely
logging into a system than telnet. As general advice, we recommend
using SSH rather than telnet.


V. References

* US-CERT Vulnerability Note VU#881872 -
<http://www.kb.cert.org/vuls/id/881872>

* Recovering from an Incident -
<http://www.cert.org/nav/recovering.html>

* Sun Alert Notification 102802 -
<http://sunsolve.sun.com/search/document.do?assetkey=1-26-102802-1>

* Solaris in.telnetd worm seen in the wild + inoculation script -
<http://blogs.sun.com/security/entry/solaris_in_telnetd_worm_seen>

* inoculate.local -
<http://blogs.sun.com/security/resource/inoculate.local>

* CVE-2007-0882 -
<http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-0882>


____________________________________________________________________

The most recent version of this document can be found at:

<http://www.us-cert.gov/cas/techalerts/TA07-059A.html>
____________________________________________________________________

Feedback can be directed to US-CERT Technical Staff. Please send
email to <cert@cert.org> with "TA07-059A Feedback VU#881872" in the
subject.
____________________________________________________________________

For instructions on subscribing to or unsubscribing from this
mailing list, visit <http://www.us-cert.gov/cas/signup.html>.
____________________________________________________________________

Produced 2007 by US-CERT, a government organization.

Terms of use:

<http://www.us-cert.gov/legal.html>
____________________________________________________________________


Revision History

February 28, 2007: Initial release


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