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             AUSCERT External Security Bulletin Redistribution

                               ESB-2016.0092
          CVE-2015-8605: UDP payload length not properly checked
                              14 January 2016

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           DHCP
Publisher:         ISC
Operating System:  Windows
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2015-8605  

Original Bulletin: 
   https://kb.isc.org/article/AA-01334/0/CVE-2015-8605%3A-UDP-payload-length-not-properly-checked.html

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CVE-2015-8605: UDP payload length not properly checked

Author: 

Brian Conry 

Reference Number: 

AA-01334 

Views: 

4346 

Created: 

2016-01-12 14:41 

Last Updated: 

2016-01-12 21:45

CVE:

CVE-2015-8605

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 2001-2015 Internet Systems Consortium

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.org. To 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
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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.

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