Message-ID: <BAY13-F94UHMuEEkHMz0005c4f7@hotmail.com>
Date: Tue, 22 Jun 2004 22:40:21 +0000
From: "System Administrator" <lowdownhaxor@...mail.com>
To: bugtraq@...urityfocus.com
Subject: DHCP Vuln // no code 0day //


Technical Cyber Security Alert TA04-174A
Multiple Vulnerabilities in ISC DHCP 3

Original release date: June 22, 2004
Last revised:  --
Source: US-CERT

Systems Affected

* ISC DHCP versions 3.0.1rc12 and  3.0.1rc13

Overview

Two vulnerabilities in the ISC  DHCP allow a remote attacker to cause a
denial of the DHCP  service on a vulnerable system. It may be possible
to exploit  these vulnerabilities to execute arbitrary code on the
system.

I. Description

As described in RFC 2131, "the  Dynamic Host Configuration Protocol
(DHCP) provides a framework  for passing configuration information to
hosts on a TCP/IP  network." The Internet Systems Consortium's (ISC)
Dynamic Host  Configuration Protocol (DHCP) 3 application contains two
vulnerabilities that present several potential buffer overflow
conditions.

VU#317350 discusses a buffer overflow  vulnerability in the temporary
storage of log lines. In  transactions, ISC DHCPD logs every DHCP
packet along with  several pieces of descriptive information. The
client's DISCOVER  and the resulting OFFER, REQUEST, ACK, and NAKs are
all logged.  In all of these messages, if the client supplied a
hostname,  then it is also included in the logged line. As part of the
DHCP  datagram format, a client may specify multiple hostname options,
up to 255 bytes per option. These options are concatenated by  the
server. If the hostname and options contain only ASCII  characters,
then the string will pass non-ASCII character  filters and be
temporarily stored in 1024 byte fixed-length  buffers on the stack. If
a client supplies enough hostname  options, it is possible to overflow
the fixed-length  buffer.

VU#654390 discusses C include files for systems that  do not support
the bounds checking vsnprintf() function. These  files define the
bounds checking vsnprintf() to the non-bounds  checking vsprintf()
function. Since vsprintf() is a function  that does not check bounds,
the size is discarded, creating the  potential for a buffer overflow
when client data is supplied.  Note that the vsnprintf() statements are
defined after the  vulnerable code that is discussed in VU#317350.
Since the  preconditions for this vulnerability are similar to those
required to exploit VU#317350, these buffer overflow conditions  occur
sequentially in the code after the buffer overflow  vulnerability
discussed in VU#317350, and these issues were  discovered and resolved
at the same time, there is no known  exploit path to exploit these
buffer overflow conditions caused  by VU#654390. Note that VU#654390
was discovered and exploitable  once VU#317350 was resolved.

For both of the  vulnerabilities, only ISC DHCP 3.0.1rc12 and ISC DHCP
3.0.1rc13  are believed to be vulnerable. VU#317350 is exploitable for
all  operating systems and configurations. VU#654390 is only defined
for the following operating systems:

* AIX
* AlphaOS
* Cygwin32
* HP-UX
* Irix
* Linux
* NextStep
* SCO
*  SunOS 4
* SunOS 5.5
*  Ultrix

All versions of ISC DCHP 3, including all snapshots,  betas, and
release candidates, contain the flawed code. However,  versions other
than ISC DHCP 3.0.1rc12 and ISC DHCP 3.0.1rc13  discard all but the
last hostname option provided by the client,  so it is not believed
that these versions are  exploitable.

US-CERT is tracking these issues as VU#317350,  which has been assigned
CVE CAN-2004-0460, and VU#654390, which  has been assigned CVE
CAN-2004-0461.

II.  Impact

Exploitation of these vulnerabilities may cause a  denial-of-service
condition to the DHCP daemon (DHCPD) and may  permit a remote attacker
to execute arbitrary code on the system  with the privileges of the
DHCPD process, typically  root.

III. Solution

Apply patches or  upgrade

These issues have been resolved in ISC DHCP  3.0.1rc14. Your vendor may
provide specific patches or updates.  For vendor-specific information,
please see your vendor's site,  or look for your vendor infomation in
VU#317350 and VU#654390.  As vendors report new information to US-CERT,
we will update the  vulnerability notes.

Appendix B. References

*  http://www.isc.org/sw/dhcp/
*  http://www.kb.cert.org/vuls/id/317350
*  http://www.kb.cert.org/vuls/id/654390
// -> 81memories.com // shouts to: myself

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