CVE-2020-12667Network attack vector

Service interruption via glueless delegation query amplification

Published May 19, 2020 · Updated Aug 4, 2024

Uncontrolled resource consumption in CZ.NIC Knot Resolver before 5.1.1 allows remote attackers to interrupt DNS service via crafted answers. The iterator follows fake glueless NS delegations by resolving attacker-supplied random names, generating many outbound queries toward victim authoritative servers. Any remote client able to query the resolver and control an authoritative server can induce tens-fold packet amplification and overload the resolver or victim DNS service.

CVSS severity7.5
High
EPSS probability2.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in CZ.NIC Knot Resolver before 5.1.1 allows remote attackers to interrupt DNS service via crafted answers. The iterator follows fake glueless NS delegations by resolving attacker-supplied random names, generating many outbound queries toward victim authoritative servers. Any remote client able to query the resolver and control an authoritative server can induce tens-fold packet amplification and overload the resolver or victim DNS service.

The record

CVE
CVE-2020-12667
Published
May 19, 2020
Updated
Aug 4, 2024
Vendor
CZ.NIC
Product
Knot Resolver
Classifications
CWE-400, T1498.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 19, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=-

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

CZ.NIC · Knot Resolverversion=-

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1498.002Network Denial of Service: Reflection Amplification

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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