CVE-2026-33254
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 · uneditedAn attacker can create a large number of concurrent DoQ or DoH3 connections, causing unlimited memory allocation in DNSdist and leading to a denial of service. DOQ and DoH3 are disabled by default.
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 confidenceDNSdist versions with DoQ (DNS over QUIC) and DoH3 (DNS over HTTP/3) enabled suffer from an uncontrolled memory allocation vulnerability. An attacker can establish a large volume of concurrent DoQ or DoH3 connections, causing the process to allocate memory without bounds until system resources are exhausted, resulting in denial of service.
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>= 1.9.0, < 1.9.13>= 2.0.0, < 2.0.4CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check installed dnsdist versionRun `dnsdist --version` to determine the exact version numberAffected if Version is 1.9.0 to 1.9.12, or 2.0.0 to 2.0.3 (the vulnerable versions)
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Locate dnsdist configuration fileCheck for configuration file at `/etc/dnsdist/dnsdist.conf` or other locations where dnsdist config is storedAffected if Configuration file exists and DoQ/DoH3 are enabled within it
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Detect if DoQ (DNS over QUIC) is enabledSearch configuration file content for `setDoQ`, `addDOQ`, or `doq` related directives. Also run `dnsdist -l 2>&1` to list listeners and check for QUIC/DNS over QUIC portsAffected if DoQ is explicitly enabled in the dnsdist configuration
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Detect if DoH3 (DNS over HTTP/3) is enabledSearch configuration file content for `setDOH3`, `addDOH3`, `doh3` or HTTP/3 related directives. Check listener output for HTTP/3 endpointsAffected if DoH3 is explicitly enabled in the dnsdist configuration
You are affected if dnsdist version is 1.9.0-1.9.12 or 2.0.0-2.0.3 AND either DoQ or DoH3 is enabled in the configuration, as the vulnerability requires one of these features to be active.
Generated from the published advisory. Verify against your own configuration.
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 · scoped1.9.132.0.4
If DoQ/DoH3 are not required, ensure they remain disabled. If enabled, apply vendor patches when available and implement connection rate limiting or max concurrent connection limits in the DNSdist configuration.
dnsdist 1.9.13 or 2.0.4 (or any later stable release)
- 1. Identify the currently installed dnsdist version using 'dnsdist --version' or package manager
- 2. If running dnsdist 1.x (>=1.9.0), upgrade to version 1.9.13 or later
- 3. If running dnsdist 2.x (>=2.0.0), upgrade to version 2.0.4 or later
- 4. Verify the new version is installed and running using 'dnsdist --version'
- 5. As a configuration-based mitigation (if upgrade is not immediately possible), ensure DoQ and DoH3 remain disabled if not explicitly needed, as they are disabled by default
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-33254 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-33254 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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