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Ubuntu LinuxOperating system · Canonical

CVE-2012-3571

MEDIUM · 6.1 CVSS v2.0 Published 2012-07-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
66/100
Remediation priority · Elevated
No privileges Zero-click

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 · unedited
ISC DHCP 4.1.2 through 4.2.4 and 4.1-ESV before 4.1-ESV-R6 allows remote attackers to cause a denial of service (infinite loop and CPU consumption) via a malformed client identifier.

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 confidence

ISC DHCP server versions 4.1.2 through 4.2.4 and 4.1-ESV before 4.1-ESV-R6 contain a flaw in client identifier processing where a malformed client identifier triggers an infinite loop, causing 100% CPU utilization and denial of service.

MitigationUpgrade to ISC DHCP 4.1-ESV-R6 or later, or 4.2.4 and later versions to resolve the vulnerability. Consider network segmentation to limit exposure until patching is possible.

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
Ubuntu LinuxOperating system
Affected:= 11.04= 11.10= 12.04
Debian LinuxOperating system
Affected:= 6.0= 7.0
DhcpApplication
Affected:= 4.1.2= 4.2.0= 4.2.1= 4.2.2= 4.2.3= 4.2.4= 4.1-esv

CVSS 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
Adjacent
Complexity
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:A/AC:L/Au:N/C:N/I:N/A:C

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 checks

Work through these to decide whether this CVE applies to you.

  1. Verify ISC DHCP server is installed
    Run 'dpkg -l | grep isc-dhcp-server' on Debian/Ubuntu, or 'rpm -qa | grep dhcp' on RHEL-based systems, or 'which dhcpd' to locate the dhcpd binary
    Affected if The package or binary is found on the system
  2. Determine the installed DHCP server version
    Run 'dhcpd --version' or 'dpkg -l isc-dhcp-server' to obtain the exact version number
    Affected if The version falls within 4.1.2 through 4.2.4, or is 4.1-ESV (any patch level before R6)
  3. Confirm the DHCP server service is running
    Run 'systemctl status isc-dhcp-server' on systemd systems, or 'service isc-dhcp-server status' on SysV init systems
    Affected if The service is active and listening for DHCP client requests
  4. Verify DHCP configuration includes client identifier processing
    Inspect /etc/dhcp/dhcpd.conf or /etc/dhcpd.conf for 'send dhcp-client-identifier' statements or client-id related options
    Affected if The server is configured to process client identifiers from DHCP requests

The system is affected if ISC DHCP server versions 4.1.2-4.2.4 or 4.1-ESV before R6 is installed, running, and configured to process client identifiers, allowing a malformed client identifier to trigger the infinite loop.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to ISC DHCP 4.1-ESV-R6 or later, or 4.2.4 and later versions to resolve the vulnerability. Consider network segmentation to limit exposure until patching is possible.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2012-3571 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data