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DnsdistApplication · Powerdns

CVE-2026-27854

HIGH · 7.5 CVSS v3.1 Published 2026-03-31
Fix available
A fix is available. Upgrade to 1.9.12 / 2.0.3 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
An attacker might be able to trigger a use-after-free by sending crafted DNS queries to a DNSdist using the DNSQuestion:getEDNSOptions method in custom Lua code. In some cases DNSQuestion:getEDNSOptions might refer to a version of the DNS packet that has been modified, thus triggering a use-after-free and potentially a crash resulting in denial of service.

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 · moderate confidence

A use-after-free vulnerability exists in DNSdist's Lua scripting interface. When custom Lua code calls DNSQuestion:getEDNSOptions on a DNSQuestion object whose underlying packet has been modified, the method may reference a freed memory region, potentially causing a crash and denial of service.

MitigationReview and update custom Lua scripts to avoid calling getEDNSOptions on modified DNSQuestion objects; apply vendor patches when available; consider restricting DNS query sources as a defense-in-depth measure.

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
DnsdistApplication
Affected:>= 1.9.0, < 1.9.12>= 2.0.0, < 2.0.3

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:3.1/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 checks

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

  1. Check dnsdist version
    Run 'dnsdist --version' or check the installed package version using your system package manager (e.g., 'dpkg -l dnsdist' or 'rpm -qi dnsdist')
    Affected if The installed version falls within >= 1.9.0, < 1.9.12 or >= 2.0.0, < 2.0.3
  2. Locate loaded Lua scripts
    Review your dnsdist configuration file (typically /etc/dnsdist/dnsdist.conf or similar) for 'loadLua', 'loadLuaFile', or 'loadPackage' directives that load custom Lua scripts
    Affected if Custom Lua scripts are loaded via configuration
  3. Identify use of vulnerable method
    Search all loaded Lua script files for the string 'getEDNSOptions' (case-sensitive)
    Affected if Any Lua script contains a call to DNSQuestion:getEDNSOptions or getEDNSOptions method on a DNSQuestion object
  4. Check for crash indicators
    Review system logs (journalctl -u dnsdist, /var/log/dnsdist.log, or syslog) for recent crashes, segfaults, or unexpected dnsdist process restarts
    Affected if Dnsdist has crashed or restarted unexpectedly since the affected version was deployed

You are affected if dnsdist version is in the vulnerable range AND custom Lua scripts using the getEDNSOptions method are loaded and actively processing DNS queries.

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.

dbcve · scoped
Upgrade available Upgrade to 1.9.12 / 2.0.3 or later
Fixed in 1.9.122.0.3
Interim mitigation

Review and update custom Lua scripts to avoid calling getEDNSOptions on modified DNSQuestion objects; apply vendor patches when available; consider restricting DNS query sources as a defense-in-depth measure.

Recommended fix High confidence

dnsdist 1.9.12 (for 1.9.x branch) or dnsdist 2.0.3 (for 2.0.x branch)

  1. 1. Identify the currently running dnsdist version using 'dnsdist --version'
  2. 2. If running dnsdist 1.9.x (versions 1.9.0-1.9.11), upgrade to dnsdist 1.9.12 or later
  3. 3. If running dnsdist 2.0.x (versions 2.0.0-2.0.2), upgrade to dnsdist 2.0.3 or later
  4. 4. After upgrade, restart the dnsdist service
  5. 5. Verify the new version is running and custom Lua scripts using DNSQuestion:getEDNSOptions work correctly
Caveat Review dnsdist release notes for 1.9.12 and 2.0.3 to check for any behavioral changes that may affect custom Lua scripts

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Dnsdist Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.

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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-2026-27854 in production — separate from our analysis above.

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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