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

  • Updated on 16 Nov 2018
  • 2 minutes to read
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CVE: CVE-2015-8605

Document version: 2.0

Posting date: 12 January 2016

Program impacted: ISC 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 Securing Your Network From DHCP Risks can substantially reduce the risk by limiting the exposure of an ISC 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 ISC DHCP. These can all be downloaded from https://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:

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 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 https://www.isc.org/downloads/.)

ISC Security Vulnerability Disclosure Policy:

Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy.

This Knowledgebase article is the complete and official security advisory document.

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