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CVE-2015-8605: UDP payload length not properly checked
Author: Brian Conry Reference Number: AA-01334 Views: 22653 Created: 2016-01-12 14:41 Last Updated: 2016-01-12 21:45 0 Rating/ Voters
Document Version:        
2.0
Posting date: 
12 January 2016
Program Impacted: 
DHCP
Versions affected: 
4.0.x, 4.1.x, 4.2.x, 4.1-ESV -> 4.1-ESV-R12, 4.3.0->4.3.3.  3.x may also be affected but has not been tested.
Severity: 
Medium
Exploitable: 
From adjacent networks

Description:

A badly formed packet with an invalid IPv4 UDP length field can cause a DHCP server, client, or relay program to terminate abnormally.

Impact:

Nearly all IPv4 DHCP clients and relays, and most IPv4 DHCP servers are potentially affected.

A server, client, or relay that is built to only be able to process unicast packets (i.e. those that have already been processed by the OS UDP/IP stack) is not affected, however this build configuration is not normally viable for clients and relays.  Servers with this build configuration require a relay in order to be able to process DISCOVER and other broadcast requests from clients.

Not all potentially-affected builds will actually be affected, but because it is difficult to identify or predict those which should be upgraded, our advice is that all builds should be considered vulnerable.

CVSS Score:  5.7

CVSS Vector:  (AV:A/AC:M/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=(AV:A/AC:M/Au:N/C:N/I:N/A:C)

Workarounds:

None likely, but in some environments following the advice from https://kb.isc.org/article/AA-00573/31/Securing-Your-Network-From-DHCP-Risks.html can substantially reduce the risk by limiting the exposure of a DHCP server to "controlled" networks and clients.

Active exploits:

No known active exploits.

Solution:  Upgrade to the patched release most closely related to your current version of DHCP. These can all be downloaded from http://www.isc.org/downloads.

  • DHCP version 4.1-ESV-R12-P1
  • DHCP version 4.3.3-P1

Acknowledgements: Thanks to Sebastian Poehn from Sophos for reporting this issue.

Document Revision History:

1.0 Advance Notification 5 January, 2016
1.1 ESV Version name corrected 12 January 2016
2.0 Public Disclosure 12 January, 2016

Related Documents:

If you'd like more information on ISC Subscription Support and Advance Security Notifications, please visit http://www.isc.org/support/.

Do you still have questions?  Questions regarding this advisory should go to security-officer@isc.orgTo report a new issue, please encrypt your message using security-officer@isc.org's PGP key which can be found here: https://www.isc.org/downloads/software-support-policy/openpgp-key/.  If you are unable to use encrypted email, you may also report new issues at: https://www.isc.org/community/report-bug/.

Note: ISC patches only currently supported versions. When possible we indicate EOL versions affected.  (For current information on which versions are actively supported, please see http://www.isc.org/downloads/). 

ISC Security Vulnerability Disclosure Policy:  Details of our current security advisory policy and practice can be found here: https://kb.isc.org/article/AA-00861/164/ISC-Software-Defect-and-Security-Vulnerability-Disclosure-Policy.html

This Knowledge Base article https://kb.isc.org/article/AA-01334 is the complete and official security advisory document.

Legal Disclaimer:
Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time.  A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors.


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