dbcve.org
FedoraOperating system · Fedoraproject

CVE-2022-40188

HIGH · 7.5 CVSS v3.1 Published 2022-09-23
Fix available
A fix is available. Upgrade to 5.5.3 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
Knot Resolver before 5.5.3 allows remote attackers to cause a denial of service (CPU consumption) because of algorithmic complexity. During an attack, an authoritative server must return large NS sets or address sets.

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

Knot Resolver before 5.5.3 contains an algorithmic complexity vulnerability where processing large NS or address sets returned from authoritative nameservers causes excessive CPU consumption, enabling remote denial of service attacks.

MitigationUpgrade to Knot Resolver 5.5.3 or later to obtain the patch. Consider implementing DNS query rate limiting or restricting acceptable response sizes as additional defensive measures.

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
FedoraOperating system
Affected:= 35= 36= 37
Debian LinuxOperating system
Affected:= 10.0
Knot ResolverApplication
Affected:< 5.5.3

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. Verify Knot Resolver is installed
    Check for the presence of the knot-resolver or kresd package using your system package manager (e.g., 'rpm -qa | grep knot' on Fedora, 'dpkg -l | grep knot-resolver' on Debian, or check for the kresd binary in common paths like /usr/sbin/kresd)
    Affected if Knot Resolver package is not found on the system, so the service is not installed and not affected
  2. Determine installed Knot Resolver version
    Run 'knot-resolver --version' or 'kresd --version' from the command line, or query the package manager (e.g., 'rpm -q knot-resolver' on Fedora, 'dpkg -s knot-resolver' on Debian) to retrieve the exact version number
    Affected if The installed version is lower than 5.5.3 (e.g., 5.5.0, 5.4.3, etc.)
  3. Confirm the service is running and active
    Check if the kresd service is active using 'systemctl status kresd' or 'systemctl status knot-resolver', or check for running processes with 'ps aux | grep kresd'
    Affected if The service is actively running and processing DNS queries, making it vulnerable to the algorithmic complexity issue when receiving large NS or address sets

A system is affected if Knot Resolver is installed and running with a version lower than 5.5.3, as this version introduced the fix for the algorithmic complexity flaw in processing large NS or address sets.

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 5.5.3 or later
Fixed in 5.5.3
Interim mitigation

Upgrade to Knot Resolver 5.5.3 or later to obtain the patch. Consider implementing DNS query rate limiting or restricting acceptable response sizes as additional defensive measures.

Recommended fix High confidence

Knot Resolver 5.5.3

  1. Update your system package repository metadata
  2. Upgrade Knot Resolver to version 5.5.3 or later using your system package manager (e.g., 'dnf update knot-resolver' for Fedora or 'apt-get update && apt-get upgrade knot-resolver' for Debian)
  3. Restart the Knot Resolver service to load the updated package
  4. Verify the installed version is 5.5.3 or later using 'knot-resolver --version' or your system's package query command

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

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

Scan for this in your stack

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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-2022-40188 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