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             AUSCERT External Security Bulletin Redistribution

                               ESB-2012.0700
    Multiple errors in ISC DHCP can cause a denial-of-service condition
                               25 July 2012

===========================================================================

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

Product:           DHCP
Publisher:         Internet Systems Consortium
Operating System:  UNIX variants (UNIX, Linux, OSX)
                   Windows
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2012-3954 CVE-2012-3571 CVE-2012-3570

Original Bulletin: 
   https://kb.isc.org/article/AA-00712/
   https://kb.isc.org/article/AA-00714/
   https://kb.isc.org/article/AA-00737/

Comment: This bulletin contains three (3) Internet Systems Consortium 
         security advisories.

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Title: ISC DHCP - An error in the handling of malformed client identifiers can 
cause a denial-of-service condition in affected servers.

CVE: CVE-2012-3571

Document Version: 2.0
Posting Date: 24 July 2012
Program Impacted: ISC DHCP
Versions Affected: All versions of 4.2 (including 4.2.x-Px) to 4.2.4;
4.1-ESV through 4.1-ESV-R5; 4.1.2, 4.1.2-P1
Severity: HIGH
Exploitable: From adjacent networks.

Description:

An error in the handling of malformed client identifiers can cause a
DHCP server running affected versions (see "Impact") to enter a state
where further client requests are not processed and the server process
loops endlessly, consuming all available CPU cycles.

Under normal circumstances this condition should not be triggered, but a
non-conforming or malicious client could deliberately trigger it in a
vulnerable server. In order to exploit this condition an attacker must
be able to send requests to the DHCP server .

Impact:

Causes the server process to loop endlessly, resulting in a denial of
service. NOTE: ISC DHCP 3.0.x and ISC DHCP 4.0.x are EOL and have not
been tested for this vulnerability. Versions of ISC DHCP that are
vulnerable to CVE-2010-2156 (including 4.1.0 through 4.1.1-P1) can be
expected to terminate unexpectedly instead of looping endlessly.

CVSS Score: 6.1

CVSS Equation: (AV:A/AC:L/Au:N/C:N/I:N/A:C) 

For more information on the Common Vulnerability Scoring System and to obtain 
your specific environmental score please visit:

http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2&vector=%28AV:N/AC:L/Au:N/C:N/I:N/A:C%29

Workarounds: none

Active Exploits: No known active exploits

Solution:

Upgrade affected systems to DHCP 4.1-ESV-R6 or DHCP 4.2.4-P1
Download from www.isc.org/downloads/all

Acknowledgement: Markus Hietava of Codenomicon CROSS project for the
find and CERT-FI for vulnerability coordination.

Document Revision History:

1.0 - 3 July 2012 Phase 1 notified
1.1 - 13 July 2012 HOLD notice sent to Phase 1 regarding new CVE being
added and new public release date
1.2 - 23 July 2012 Phase 2 & 3 notified
2.0 - 24 July 2012 Phase 4-Public release

==============================================================

Title: An error in the handling of an unexpected client identifiers can cause 
a server crash when serving DHCPv6.

CVE: CVE-2012-3570

Document Version: 2.0
Posting Date: 24 July, 2012
Program Impacted: ISC DHCP
Versions Affected: 4.2.x (all versions)
Severity: HIGH
Exploitable: From adjacent networks.

Description:

An unexpected client identifier parameter can cause the ISC DHCP daemon
to segmentation fault when running in DHCPv6 mode, resulting in a denial
of service to further client requests. In order to exploit this
condition, an attacker must be able to send requests to the DHCP server.

Impact: 

Causes the server process to crash when a buffer is overflowed, resulting in 
a denial of service. NOTE: DHCP versions 4.0 -->4.1.x are NOT impacted.

CVSS Score: 6.1

CVSS Equation: (AV:A/AC:L/Au:N/C:N/I:N/A:C)

For more information on the Common Vulnerability Scoring System and to obtain 
your specific environmental score please visit:

http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2&vector=%28AV:N/AC:L/Au:N/C:N/I:N/A:C%29

Workarounds: None

Active Exploits: No known active exploits

Solution:

Upgrade affected systems to DHCP 4.2.4-P1
Download from www.isc.org/downloads/all

Acknowledgement: Markus Hietava of Codenomicon CROSS project for the
find and CERT-FI for vulnerability coordination.

Document Revision History:

1.0 - 3 July 2012 Phase 1 notified
1.1 - 13 July 2012 HOLD notice sent to Phase 1 regarding new CVE being
added and new public release date
1.2 - 23 July 2012 Phase 2 & 3 notified
2.0 - 24 July 2012 Phase 4-Public release

==============================================================

Title: Memory Leaks Found In ISC DHCP

Summary:

Two memory leaks have been found and fixed in ISC DHCP. Both are
reproducible when running in DHCPv6 mode (with the -6 command-line
argument.) The first leak is confirmed to only affect servers operating
in DHCPv6 mode, but based on initial code analysis the second may
theoretically affect DHCPv4 servers (though this has not been demonstrated.)

CVE: CVE-2012-3954

Document Version: 2.0
Posting date: 24 July 2012
Program Impacted: ISC DHCP 4
Versions affected: 4.1.x, 4.2.x
Severity: Medium
Exploitable: From networks permitted to send requests to the DHCP server.

Description:

ISC has discovered and fixed two memory leaks in the DHCP code. One of
the leaks only affects servers running in DHCPv6 mode. The other is
known to affect a server running in DHCPv6 mode but could potentially
occur on servers running in DHCPv4 mode as well. In both cases the
server can leak a small amount of memory while processing messages. The
amount leaked per iteration is small and the leak will not cause
problems in many cases. However on a server that is run for a long
period without re-starting or a server handling an extraordinary amount
of traffic from the clients the leak could consume all memory available
to the DHCP server process, preventing further operation by the DHCP
server process and potentially interfering with other services hosted on
the same server hardware.

Note: Under ISC's disclosure policy, this issue would not normally
require an advisory but we are issuing one in this case in coordination
with other security issues being disclosed at this time. DHCP 3.1-ESV
has not been tested for this issue but examination of the code suggests
that it is potentially vulnerable. All versions of ISC DHCP 3 are
currently beyond the end of their support from ISC and we will not be
releasing patches for these "End of Life" (EOL) versions.

CVSS Score: 3.3

CVSS Equation: (AV:A/AC:L/Au:N/C:N/I:N/A:P)

For more information on the Common Vulnerability Scoring System and to obtain 
your specific environmental score please visit:

http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2&vector=%28AV:A/AC:L/Au:N/C:N/I:N/A:P%29

Workarounds:

Restarting the server at periodic intervals will address the problem
sufficiently in most operational environments. Where DHCP traffic is
permitted from hosts not under the control of the network operator (e.g.
open or semi-public networks) upgrading is more strongly recommended.

Solution: 

Upgrade to ISC DHCP 4.1-ESV-R6 or 4.2.4-P1
Download 4.2.4-P1 or 4.1-ESV-R6 from www.isc.org/downloads/all

Exploit Status: No known active exploits

Acknowledgment: ISC would like to thank Glen Eustace of Massey
University, New Zealand for finding this issue.

Document Revision History:

1.0 - 11 July, 2012 - Phase 1 contacted
1.1 - 17 July, 2012. - Phase 1 re-issued, re-released patch with
additional code
1.2 - 23 July, 2012 - Phase 2 & 3 notification sent
2.0 - 24 July, 2012 Phase 4-Public release

References:

Do you have Questions? Questions regarding this advisory should go
to security-officer@isc.org.

ISC Security Vulnerability Disclosure Policy: Details of our current
security advisory policy and practice can be found here:
https://www.isc.org/security-vulnerability-disclosure-policy

If you'd like more information on our Forum or BIND/DHCP support please
visit http://www.isc.org/software/guild or http://www.isc.org/support

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A stand-alone copy or paraphrase of the text of this document that omits
the distribution URL in the following section is an uncontrolled copy.
Uncontrolled copies may lack important information, be out of date, or
contain factual errors.

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