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CVE-2013-2494: A Vulnerability in libdns Could Cause Excessive Memory Use in ISC DHCP 4.2
Author: Michael McNally Reference Number: AA-00880 Views: 76184 Created: 2013-03-18 07:35 Last Updated: 2013-09-04 15:52 0 Rating/ Voters

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 ISC DHCP 4.2.

Document Version:          
Posting date: 
26 March 2013
Program Impacted: 
Versions affected: 
4.2.0 -> 4.2.5.  ISC DHCP versions prior to 4.2.0 (including 4.1-ESV) are not affected.
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:



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]

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