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CVE-2018-5733: A malicious client can overflow a reference counter in ISC dhcpd
Author: Michael McNally Reference Number: AA-01567 Views: 19492 Created: 2018-02-21 23:45 Last Updated: 2018-02-28 15:28 0 Rating/ Voters
Document Version: 
2.0
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 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-01567 is the complete and official security advisory document.

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