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

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Article Summary

CVE: CVE-2018-5732

Document version: 2.0

Posting date: 28 February 2018

Program impacted: ISC 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


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.


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 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 cannot rule it out as impossible. The safest course is to patch dhclient so that the buffer overflow cannot occur.

CVSS Score: 7.5


For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit:

Workarounds: None.

Active exploits: No known active exploits.

Solution: Upgrade to the patched release most closely related to your current version of DHCP. These are all available at

  • 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

Related documents:

See our BIND 9 Security Vulnerability Matrix for a complete listing of security vulnerabilities and versions affected.

Do you still have questions? Questions regarding this advisory should go to To report a new issue, please encrypt your message using's PGP key which can be found here: If you are unable to use encrypted email, you may also report new issues at:


ISC patches only currently supported versions. When possible we indicate EOL versions affected. (For current information on which versions are actively supported, please see

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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