CRIME FW: US-CERT Technical Cyber Security Alert TA04-174A -- Multiple Vulnerabilities in ISC DHCP 3

From: George Heuston (GeorgeH@private)
Date: Tue Jun 22 2004 - 14:25:31 PDT

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    -----Original Message-----
    From: US-CERT Technical Alerts [] 
    Sent: Tuesday, June 22, 2004 11:18 AM
    Subject: US-CERT Technical Cyber Security Alert TA04-174A -- Multiple
    Vulnerabilities in ISC DHCP 3 
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                   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
       Two vulnerabilities in the ISC DHCP allow a remote attacker to cause
       denial of the DHCP service on a vulnerable system. It may be possible
       to exploit these vulnerabilities to execute arbitrary code on the
    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
       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
       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
       CVE CAN-2004-0460, and VU#654390, which has been assigned CVE
    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
       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
       we will update the vulnerability notes.
    Appendix B. References
       US-CERT thanks Gregory Duchemin and Solar Designer for discovering,
       reporting, and resolving this vulnerability. Thanks also to David
       Hankins of ISC for notifying us of this vulnerability and the
       technical information provided to create this document.
       Feedback can be directed to the author: Jason A. Rafail
       The latest version of this document can be found at:
       Copyright 2004 Carnegie Mellon University.
       Terms of use:
       Revision History
       June 22, 2004: Initial release
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