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             AUSCERT External Security Bulletin Redistribution

           CVE-2013-2494: A Vulnerability in libdns Could Cause
                   Excessive Memory Use in ISC DHCP 4.2
                               2 April 2013


        AusCERT Security Bulletin Summary

Product:           DHCP
Operating System:  UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2013-2494  

Original Bulletin: 

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CVE-2013-2494: A Vulnerability in libdns Could Cause Excessive Memory Use in 

A memory exhaustion bug has been discovered in libdns, which is used by ISC 
DHCP 4.2. Theoretically this could be exploited to cause memory exhaustion in

CVE: 			CVE-2013-2494
Document Version:       2.0
Posting date: 		26 March 2013
Program Impacted: 	ISC DHCP
Versions affected: 	4.2.0 -> 4.2.5.  ISC DHCP versions prior to 4.2.0 
			(including 4.1-ESV) are not affected.
Severity: 		Low
Exploitable: 		From adjacent networks


Exploitation of a memory exhaustion bug in libdns is theoretically possible in
ISC DHCP 4.2, which uses the library from BIND 9 for Dynamic DNS.

Unlike vulnerabilities which can be exercised by a machine impersonating a 
malicious client, exploitation of this vulnerability is complex and requires 
either controlling a nameserver with whom the DHCP server process is 
communicating or successfully spoofing traffic to appear as such. These 
preconditions result in a CVSS severity of "Low", but operators using 
vulnerable versions of DHCP 4.2 are nevertheless recommended to upgrade to 
DHCP 4.2.5-P1, which prevents exploitation of the libdns library defect.


Servers which are targeted by a successful attack will exhaust all memory 
available to the server process, which is likely to crash the DHCP server and
may affect other processes running on the same physical machine when system 
memory is exhausted.

CVSS Score:  		4.9

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

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


None.  (Or do we want to mention that you can change the build process for 
the BIND libraries?)

Active exploits:

No known active exploits.

Solution:  Upgrade to DHCP 4.2.5-P1

Document Revision History:

1.0 Phase One - Advance Notification, 18 March 2013

1.2 Phase Two & Three Notification, 25 March 2013

2.0 Public notification, 26 March 2013

Related Documents:

Japanese Translation:  [planned]
Spanish Translation:  [planned]
German Translation:  [planned]
Portugese Translation:  [planned]

If you'd like more information on our Forum or product support please visit 

Do you still have questions?  Questions regarding this advisory should go to 

Note: ISC patches only currently supported versions. When possible we indicate
EOL versions affected.

ISC Security Vulnerability Disclosure Policy:  Details of our current security 
advisory policy and practice can be found here: 

This Knowledge Base article https://kb.isc.org/article/AA-00880 is the complete 
and official security advisory document.

Legal Disclaimer:
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absence of hidden defects, or of non-infringement. Your use or reliance on this
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Uncontrolled copies may lack important information, be out of date, or contain 
factual errors.

© 2001-2013 Internet Systems Consortium

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