CVE-2018-5732: A specially constructed response from a malicious server can cause a buffer overflow in dhclient
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
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
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.
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 https://www.isc.org/downloads.
- 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
See our BIND 9 Security Vulnerability Matrix for a complete listing of security vulnerabilities and versions affected.
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ISC patches only currently supported versions. When possible we indicate EOL versions affected. (For current information on which versions are actively supported, please see https://www.isc.org/downloads/.)
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.
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