Knowledge Base ISC Main Website Ask a Question/Contact ISC
CVE-2012-3571: An Error in the Handling of Malformed Client Identifiers can Cause a Denial-of-Service Condition in Affected Servers
Author: Michael McNally Reference Number: AA-00712 Views: 4319 Created: 2012-07-02 23:44 Last Updated: 2012-07-30 19:14 0 Rating/ Voters

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

Document Version:          
Posting date: 
24 Jul 2012
Program Impacted: 
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
Locally - From adjacent networks


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 .


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



Active exploits: 

None known at this time.


Upgrade affected systems to DHCP 4.1-ESV-R6 or DHCP 4.2.4-P1

DHCP 4.2.4-P1 is available from

DHCP 4.1-ESV-R6 is available from

Markus Hietava of Codenomicon CROSS project for finding the vulnerability, and CERT-FI for vulnerability coordination.

Document Revision History:

1.0 - 03 July 2012 Phase I 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 released
2.1 - 30 July 2012 Added Chinese translation


© 2001-2014 Internet Systems Consortium

  • Please help us to improve the content of our knowledge base by letting us know how we can improve this article or by submitting suggestions for other articles you'd like to see created. Information on how to obtain further help on our products or services can be found on our main website.' If you have a technical question or problem on which you'd like help, we recommend searching our community mailing list archives and/or posting your question there (you will need to register there first for your posts to be accepted). The bind-users and the dhcp-users lists particularly have a long-standing and active membership.
Info Submit Feedback on this Article
Nickname: Your Email: Subject: Comment:
Enter the code below:
Quick Jump Menu