CVE-2018-5733: A malicious client can overflow a reference counter in ISC dhcpd

[Michael McNally]

CVE:                 CVE-2018-5733
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:            Medium
Exploitable:         Remotely

Description:

   A malicious client which is allowed to send very large amounts
   of traffic (billions of packets) to a DHCP server can eventually
   overflow a 32-bit reference counter, potentially causing dhcpd
   to crash.

Impact:

   Successful exploitation of this vulnerability may exhaust the
   memory available to dhcpd and/or cause it to crash, resulting
   in a denial of service to clients.

CVSS Score:          5.9
CVSS Vector:         CVSS:3.0/AV:N/AC:H/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:H/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
   2.0 Public Disclosure 28 February 2018

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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
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   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-01567 is
the complete and official security advisory document.

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