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NsdApplication · Nlnetlabs

CVE-2016-6173

HIGH · 7.5 CVSS v3.0 Published 2017-02-09
Fix available
A fix is available. Upgrade to after 4.1.10 or later.
See remediation →
84/100
Remediation priority · High
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
NSD before 4.1.11 allows remote DNS master servers to cause a denial of service (/tmp disk consumption and slave server crash) via a zone transfer with unlimited data.

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

NSD before version 4.1.11 contains a vulnerability where remote DNS master servers can trigger a denial of service by sending zone transfers with unlimited data, causing excessive disk consumption in /tmp and potential slave server crashes.

MitigationUpgrade NSD to version 4.1.11 or later to obtain the patch that limits zone transfer data size.

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
NsdApplication
Affected:<= 4.1.10

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. Check installed NSD version
    Run 'nsd -v' or 'nsd -h' to display version information, or check your package manager for nsd version
    Affected if Version is 4.1.10 or lower
  2. Verify NSD is configured as a slave server
    Inspect NSD configuration file (typically /etc/nsd/nsd.conf) for 'zone' entries with 'allow-transfer' or 'request-xfr' directives that enable incoming zone transfers from remote masters
    Affected if NSD is configured to receive zone transfers from remote DNS masters
  3. Check for excessive /tmp disk usage
    Run 'df -h /tmp' to check disk usage, and list recent files in /tmp with 'ls -lat /tmp | head -20' looking for large zone transfer temporary files
    Affected if /tmp contains unexpectedly large files or is nearly full due to zone transfer data
  4. Check NSD logs for zone transfer issues
    Review NSD logs (typically /var/log/nsd.log or /var/log/messages) for entries indicating excessive zone transfer activity, disk full errors, or crash events
    Affected if Logs show zone transfer activity causing disk issues or NSD crashes

You are affected if NSD version 4.1.10 or lower is installed and configured to receive zone transfers from remote masters, with symptoms including /tmp disk consumption or slave server instability.

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 4.1.10
Interim mitigation

Upgrade NSD to version 4.1.11 or later to obtain the patch that limits zone transfer data size.

Fix this in Nsd Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

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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-2016-6173 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