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DnsdistApplication · Powerdns

CVE-2026-27853

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 an out-of-bounds write by sending crafted DNS responses to a DNSdist using the DNSQuestion:changeName or DNSResponse:changeName methods in custom Lua code. In some cases the rewritten packet might become larger than the initial response and even exceed 65535 bytes, potentially leading to 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 · high confidence

Out-of-bounds write vulnerability in DNSdist's Lua scripting engine where DNSQuestion:changeName and DNSResponse:changeName methods allow attackers to expand DNS response packets beyond their allocated buffer size. Crafted DNS responses can cause rewritten packets to exceed 65535 bytes, triggering heap corruption and potential denial of service via crash.

MitigationAvoid processing untrusted DNS responses with custom Lua scripts using changeName methods; update DNSdist to patched version when available; consider disabling Lua scripting if not required.

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 installed Dnsdist version
    Run 'dnsdist --version' or check package manager (dpkg -l pdns-dnsdist, rpm -q dnsdist) to get the exact version number
    Affected if Version is >= 1.9.0 and < 1.9.12, or >= 2.0.0 and < 2.0.3
  2. Verify Lua scripting is enabled
    Inspect dnsdist configuration file (typically /etc/dnsdist/dnsdist.conf) for setLua(), setLuaCPredis(), or loadClassicDNSBackend() directives that enable custom Lua code execution
    Affected if Lua scripting is enabled and custom scripts are loaded via configuration
  3. Identify Lua scripts using changeName methods
    Search all .lua script files referenced in dnsdist configuration for occurrences of 'DNSQuestion:changeName' or 'DNSResponse:changeName'
    Affected if Any custom Lua script contains these methods that manipulate DNS packet names in responses
  4. Check if Lua scripts process remote DNS responses
    Review Lua script logic to determine if changeName is applied to responses received from upstream servers (not just locally generated)
    Affected if changeName method is used to rewrite response packets from upstream resolvers

Environment is affected if running a vulnerable Dnsdist version AND custom Lua scripts using DNSQuestion:changeName or DNSResponse:changeName process DNS responses from upstream servers.

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

Avoid processing untrusted DNS responses with custom Lua scripts using changeName methods; update DNSdist to patched version when available; consider disabling Lua scripting if not required.

Recommended fix High confidence

Upgrade to dnsdist 1.9.12 (for 1.9.x users) or dnsdist 2.0.3+ (for 2.0.x users)

  1. 1. Identify your current dnsdist version using 'dnsdist --version'
  2. 2. If running dnsdist 1.9.x (>=1.9.0, <1.9.12): upgrade to version 1.9.12 or later
  3. 3. If running dnsdist 2.0.x (>=2.0.0, <2.0.3): upgrade to version 2.0.3 or later
  4. 4. For package-based installations: update via your distribution's package manager (e.g., apt-get update && apt-get install dnsdist)
  5. 5. For source installations: download the fixed release from the dnsdist repository and recompile
  6. 6. After upgrade, restart the dnsdist service
  7. 7. Verify the new version is running: 'dnsdist --version'

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

Fix this in Dnsdist Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.

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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-2026-27853 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