CVE-2012-3954: Memory Leaks Found in ISC DHCP
  • 30 Jul 2012
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CVE-2012-3954: Memory Leaks Found in ISC DHCP

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Title:  Memory Leaks Found In ISC DHCP


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:  2.1

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.


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:


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

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 2.1 - 30 July, 2012 - Added Chinese translation


- Do you have Questions?  Questions regarding this advisory should go to

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

- Japanese Translation: - Spanish Translation :

- German Translation :

- Chinese Translation :

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