CVE-2018-5732: A specially constructed response from a malicious server can cause a buffer overflow in dhclient

Michael McNally mcnally at isc.org
Wed Feb 28 17:19:34 UTC 2018


CVE:                 CVE-2018-5732
Document Version:    1.0
Posting date:        28 February 2018
Program Impacted:    DHCP
Versions affected:   4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8,
                     4.3.0 -> 4.3.6, 4.4.0
Severity:            High
Exploitable:         Remotely

Description:

   Failure to properly bounds check a buffer used for processing
   DHCP options allows a malicious server (or an entity masquerading
   as a server) to cause a buffer overflow (and resulting crash)
   in dhclient by sending a response containing a specially constructed
   options section.

Impact:

   Affected versions of dhclient should crash due to an out-of-bounds
   memory access if they receive and process a triggering response
   packet.  However, buffer overflow outcomes can vary by operating
   system and outcomes such as such as remote code execution may
   be possible in some circumstances.  Where they are present,
   operating system mitigation strategies such as address space
   layout randomization (ASLR) should make it difficult to leverage
   this vulnerability to achieve remote code execution but we can
   not rule it out as impossible.  The safest course is to patch
   dhclient so that the buffer overflow cannot occur.

CVSS Score:          7.5
CVSS Vector:         CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Workarounds:         None.
Active exploits:     No known active exploits.

Solution:

   Upgrade to the patched release most closely related to your
   current version of DHCP.

   - DHCP 4.1-ESV-R15-P1
   - DHCP 4.3.6-P1
   - DHCP 4.4.1

Acknowledgements:

   ISC would like to thank Felix Wilhelm, Google Security Team, for
   reporting this vulnerability.

Document Revision History:

   1.0 Advance Notification 21 February 2018
   1.1 Strengthened language in "Impact" section 27 February 2018
   2.0 Public Disclosure 28 February 2018

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 at isc.org.  To report a new issue,
please encrypt your message using security-officer at 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

This Knowledge Base article https://kb.isc.org/article/AA-01565 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.

(c) 2001-2018 Internet Systems Consortium


More information about the dhcp-announce mailing list