CVE-2018-5732
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedFailure 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
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceBuffer overflow vulnerability in ISC DHCP client's dhclient when processing DHCP options from server responses. A malicious DHCP server (or attacker spoofing responses) can send specially crafted oversized options that overflow an internal buffer, causing dhclient to crash.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 4.1.0, <= 4.1.2>= 4.2.0, < 4.2.8>= 4.3.0, < 4.3.6= 4.1-esv= 4.1.2= 4.4.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check if dhclient is installedRun 'which dhclient' or 'find /usr -name dhclient 2>/dev/null' to locate the dhclient binaryAffected if dhclient binary is not found - not vulnerable because the client is not installed
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Identify dhclient versionRun 'dhclient -v' or 'dhclient --version' to obtain the exact version numberAffected if version matches any of these ranges: 4.1.0-4.1.2, 4.2.0-4.2.7, 4.3.0-4.3.5, 4.1-ESV (any patch), 4.4.0
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Verify dhclient is actively usedCheck if dhclient process is running: 'ps aux | grep dhclient' or check network interfaces for DHCP client lease files in /var/lib/dhclient/ or /var/lib/dhcp/Affected if dhclient is not running and no lease files exist - not currently vulnerable as the client is not active
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Confirm ISC DHCP implementationCheck package manager output: 'rpm -qi dhclient' (RHEL/CentOS), 'dpkg -l | grep isc-dhcp' (Debian), or examine dhclient binary with 'file $(which dhclient)'Affected if the dhclient is from an ISC DHCP package and version falls within affected ranges
You are affected if you have an ISC dhclient version within 4.1.0-4.1.2, 4.2.0-4.2.7, 4.3.0-4.3.5, 4.1-ESV, or 4.4.0 actively running as your DHCP client.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data4.2.84.3.6
Primary: Upgrade to patched ISC DHCP version beyond 4.1-ESV-R15/4.2.8/4.3.6/4.4.0. Secondary: Enable DHCP snooping on network switches to block rogue DHCP servers, or implement DHCP authentication where supported.
- Consultation3.0 h
- Implementation2.0 h
- Testing6.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-5732 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-5732 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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