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Ubuntu LinuxOperating system · Canonical

CVE-2017-13704

HIGH · 7.5 CVSS v3.0 Published 2017-10-03
Fix available
A fix is available. Upgrade to after 2.77 or later.
See remediation →
84/100
Remediation priority · High
High EPSS Remotely reachable 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
In dnsmasq before 2.78, if the DNS packet size does not match the expected size, the size parameter in a memset call gets a negative value. As it is an unsigned value, memset ends up writing up to 0xffffffff zero's (0xffffffffffffffff in 64 bit platforms), making dnsmasq crash.

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

In dnsmasq before 2.78, when processing DNS packets that are smaller than expected, a negative size value is passed to memset. Due to type conversion from signed to unsigned, this becomes a very large positive value (0xffffffff/0xffffffffffffffff), causing memset to write an enormous amount of data and crash the dnsmasq service.

MitigationUpgrade dnsmasq to version 2.78 or later. As a workaround, implement network-level filtering to block malformed DNS packets before they reach dnsmasq.

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:= 14.04= 16.04= 17.04
Debian LinuxOperating system
Affected:= 7.0= 7.1= 9.0
FedoraOperating system
Affected:= 27
Enterprise Linux DesktopOperating system
Affected:= 7.0
Enterprise Linux ServerOperating system
Affected:= 7.0
Enterprise Linux WorkstationOperating system
Affected:= 7.0
LeapOperating system
Affected:= 42.2= 42.3
DnsmasqApplication
Affected:<= 2.77

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/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 checks

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

  1. Identify installed dnsmasq version
    Run 'dnsmasq --version' or check the package manager: 'dpkg -l dnsmasq' (Debian/Ubuntu), 'rpm -q dnsmasq' (RHEL/Fedora), or 'zypper se dnsmasq' (Novell Leap)
    Affected if The version number returned is less than 2.78 (e.g., 2.77, 2.76, etc.) or the package is from an affected release listed in the CVE
  2. Confirm dnsmasq service is active
    Check if the dnsmasq service is running: 'systemctl status dnsmasq' (systemd) or 'service dnsmasq status' (SysVinit)
    Affected if The service is running and processing DNS queries - only then can the malformed packet flaw be triggered
  3. Verify DNS service binding
    Check if dnsmasq is listening on DNS ports (53/UDP or 53/TCP) using 'netstat -ulnp | grep :53' or 'ss -ulnp | grep :53'
    Affected if dnsmasq is bound to port 53, exposing the service to network traffic and the vulnerability
  4. Check DNS packet handling config
    Review dnsmasq configuration in /etc/dnsmasq.conf or /etc/dnsmasq.d/ for any non-default settings that affect DNS packet processing; verify with 'dnsmasq --test' that config loads without errors
    Affected if The service is configured to handle DNS queries (default behavior when port 53 is in use)

You are affected if dnsmasq is running and the installed version is 2.77 or earlier (or from an older package of an affected distribution), since the flaw triggers when malformed DNS packets smaller than expected are processed.

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
Upgrade available Upgrade to a release after 2.77
Interim mitigation

Upgrade dnsmasq to version 2.78 or later. As a workaround, implement network-level filtering to block malformed DNS packets before they reach dnsmasq.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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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-2017-13704 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