CVE-2022-40188Network attack vector

DNS service interruption via unbounded nameserver sets

Published Sep 23, 2022 · Updated May 27, 2025

Algorithmic-complexity denial of service in CZ.NIC Knot Resolver before 5.5.3 allows remote attackers to exhaust CPU via DNS replies. The zone-cut and iterator paths process attacker-controlled NS records and associated A/AAAA glue without practical count limits. Exploitation requires an authoritative server to return a large nameserver or address set, causing sustained CPU consumption and interrupting DNS resolution.

CVSS severity7.5
High
EPSS probability1.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Algorithmic-complexity denial of service in CZ.NIC Knot Resolver before 5.5.3 allows remote attackers to exhaust CPU via DNS replies. The zone-cut and iterator paths process attacker-controlled NS records and associated A/AAAA glue without practical count limits. Exploitation requires an authoritative server to return a large nameserver or address set, causing sustained CPU consumption and interrupting DNS resolution.

The record

CVE
CVE-2022-40188
Published
Sep 23, 2022
Updated
May 27, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-407, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2022CVE publishedPublication date reported by the CVE source.
  2. May 27, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-407Inefficient Algorithmic Complexity
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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