Operating System:

Published:

29 August 2001

Protect yourself against future threats.

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             AUSCERT External Security Bulletin Redistribution

        ESB-2001.369 -- Internet Security Systems Security Advisory
      Remote Buffer Overflow Vulnerability in BSD Line Printer Daemon
                              30 August 2001

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:                in.lpd
Operating System:       OpenBSD CURRENT and earlier
                        FreeBSD 4.3 and earlier
                        NetBSD 1.5.1 and earlier
                        BSD/OS 4.1 and earlier
Impact:                 Root Compromise
Access Required:        Remote

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Internet Security Systems Security Advisory
August 29, 2001

Remote Buffer Overflow Vulnerability in BSD Line Printer Daemon

Synopsis:

Internet Security Systems (ISS) X-Force has discovered a vulnerability
in several BSD implementations.  A buffer overflow vulnerability exists
in the BSD Unix line printer daemon ("in.lpd" or "lpd").  Remote or local
attackers may use this vulnerability to execute arbitrary code with
superuser privilege on a vulnerable target.  

Affected Versions:

OpenBSD CURRENT and earlier
FreeBSD 4.3 and earlier
NetBSD 1.5.1 and earlier
BSD/OS 4.1 and earlier

BSD/OS 4.2 is not vulnerable

Description:

The line printer daemon is used to allow heterogeneous Unix environments
to share printers over a network.  The line printer daemon passes
network print jobs to a printer, manages printer queues, and provides
printer job control functions.

The vulnerability presents itself when an attacker submits a specially-
crafted, incomplete print job.  An attacker can subsequently request a 
display of the printer queue to trigger a buffer overflow.  A static
buffer overflow condition exists in the functionality that parses the
attacker's first request.  Attackers may use this overflow to execute
arbitrary commands on the system, or spawn an interactive shell and
then navigate the filesystem.  After the attacker successfully exploits
the buffer overflow, all commands are executed with superuser privilege.

The line printer must be enabled and configured for attackers to exploit
this vulnerability.  FreeBSD and OpenBSD do not enable in.lpd by
default.  BSD/OS line printer daemon is running by default, but with an
empty configuration file. The attacker must launch his attack from a
system that is listed in the "/etc/hosts.equiv" or "/etc/hosts.lpd" file
of the target system.

Recommendations:

ISS X-Force recommends that all administrators who have not implemented
network printing should immediately disable the line printer daemon, as
well as any other unused services.  If administrators have implemented
network printing, X-Force recommends against granting blanket access to
printers.

Patches will be made available by all the affected vendors.  Please
refer to the following addresses for patch information regarding this
vulnerability:

http://www.BSDI.COM/services/support/patches/patches-4.1/M410-044
http://www.openbsd.com/errata.html
http://www.netbsd.org/security
http://www.freebsd.org/security

ISS X-Force will provide detection and assessment support for this
vulnerability in upcoming X-Press Updates for RealSecure Network
Sensor and Internet Scanner. 

Additional Information:

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2001-0670 to this issue. This is a candidate for inclusion in
the CVE list http://cve.mitre.org, which standardizes names for security
problems.

Credits:

This vulnerability was discovered and researched by Mark Dowd of Internet
Security Systems. ISS would like to thank OpenBSD, NetBSD, FreeBSD, and
BSD/OS for their response and handling of this vulnerability.

_______

About Internet Security Systems (ISS)
Internet Security Systems is a leading global provider of security
management solutions for the Internet, protecting digital assets and
ensuring safe and uninterrupted e-business. With its industry-leading
intrusion detection and vulnerability assessment, remote managed
security services, and strategic consulting and education offerings, ISS
is a trusted security provider to more than 8,000 customers worldwide
including 21 of the 25 largest U.S. commercial banks and the top 10 U.S.
telecommunications companies. Founded in 1994, ISS is headquartered in
Atlanta, GA, with additional offices throughout North America and
international operations in Asia, Australia, Europe, Latin America and
the Middle East. For more information, visit the Internet Security
Systems web site at www.iss.net or call 888-901-7477.

Copyright (c) 2001 Internet Security Systems, Inc.

Permission is hereby granted for the redistribution of this Alert
electronically. It is not to be edited in any way without express
consent of the X-Force. If you wish to reprint the whole or any part
of this Alert in any other medium excluding electronic medium, please
e-mail xforce@iss.net for permission.

Disclaimer

The information within this paper may change without notice. Use of
this information constitutes acceptance for use in an AS IS condition.
There are NO warranties with regard to this information. In no event
shall the author be liable for any damages whatsoever arising out of or
in connection with the use or spread of this information. Any use of
this information is at the user's own risk.

X-Force PGP Key available at: http://xforce.iss.net/sensitive.php
as well as on MIT's PGP key server and PGP.com's key server.

Please send suggestions, updates, and comments to: X-Force
xforce@iss.net of Internet Security Systems, Inc.

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