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CVE-2018-5732

A specially constructed response from a malicious server can cause a buffer overflow in dhclient

High7.5EPSS 5.2%
Published
Updated
Reserved
Assigned by
isc

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. Affects ISC DHCP versions 4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8, 4.3.0 -> 4.3.6, 4.4.0

Scores

CVSS scores of CVE-2018-5732, by who scored it
Scored byCVSSScoreVector
iscCNA (assigner)3.0High7.5CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Modified3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
5.2% · top 7.4% of all CVEs (4 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

  • 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.
  • CWE-119 (opens in a new tab)All about CWE-119 and its CVEs

Affected products

  • ISC · ISC DHCP

    • affected ISC DHCP 4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8, 4.3.0 -> 4.3.6, 4.4.0

What to do

Solution: Upgrade to the patched release most closely related to your current version of DHCP. ISC DHCP releases are available from https://www.isc.org/downloads. >= DHCP 4.1-ESV-R15-P1 >= DHCP 4.3.6-P1 >= DHCP 4.4.1

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .