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CVE-2018-5732: A specially constructed response from a malicious server can cause a buffer overflow in dhclient
Author: Michael McNally Reference Number: AA-01565 Views: 22721 Created: 2018-02-21 23:23 Last Updated: 2018-02-28 15:29 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: 
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

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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-01565 is the complete and official security advisory document.

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