How severe is CVE-2020-12667?

CVE-2020-12667 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2020-12667 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-12667?

CVE-2020-12667 affects Nic Knot Resolver. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-12667?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-12667 published?

CVE-2020-12667 was published on 2020-05-19 and last updated on 2026-06-17.

CVE-2020-12667

CVE-2020-12667 is a high-severity vulnerability in Nic Knot Resolver with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (84th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Nic Knot Resolver
Published: 2020-05-19
Last modified: 2026-06-17

Description

Knot Resolver before 5.1.1 allows traffic amplification via a crafted DNS answer from an attacker-controlled server, aka an "NXNSAttack" issue. This is triggered by random subdomains in the NSDNAME in NS records.

Frequently asked questions

What is CVE-2020-12667?: Knot Resolver before 5.1.1 allows traffic amplification via a crafted DNS answer from an attacker-controlled server, aka an "NXNSAttack" issue. This is triggered by random subdomains in the NSDNAME in NS records.
How severe is CVE-2020-12667?: CVE-2020-12667 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2020-12667 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-12667?: CVE-2020-12667 affects Nic Knot Resolver. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-12667?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-12667 published?: CVE-2020-12667 was published on 2020-05-19 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nic:knot_resolver:*:*:*:*:*:*:*:*

More vulnerabilities in Nic Knot Resolver

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CVE-2022-40188 — High (CVSS 7.5): Knot Resolver before 5.5.3 allows remote attackers to cause a denial of service (CPU consumption) because of…
CVE-2021-40083 — High (CVSS 7.5): Knot Resolver before 5.3.2 is prone to an assertion failure, triggerable by a remote attacker in an edge case (NSEC3…
CVE-2018-1110 — High (CVSS 7.5): A flaw was found in knot-resolver before version 2.3.0. Malformed DNS messages may cause denial of service.

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