CVE-2020-12667

Name: CVE-2020-12667
Creator: NVD / NIST
Published: 2020-05-19T13:15:11.763+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 2.62%

Last modified Jun 17, 2026

CVE-2020-12667 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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.. EPSS estimates a 2.62% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

2.62%

83.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Nic	Knot Resolver	< 5.1.1

References

http://cyber-security-group.cs.tau.ac.il/#Technical Description, Third Party Advisory
http://www.openwall.com/lists/oss-security/2020/05/19/2Mailing List, Third Party Advisory
https://en.blog.nic.cz/2020/05/19/nxnsattack-upgrade-resolvers-to-stop-new-kind-of-random-subdomain-attack/Technical Description, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2024/04/msg00017.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/76Y4FITMOH6RVPWAANGV7NB2ZHPJJGDQ/
https://www.knot-resolver.cz/2020-05-19-knot-resolver-5.1.1.htmlRelease Notes, Vendor Advisory
http://cyber-security-group.cs.tau.ac.il/#Technical Description, Third Party Advisory
http://www.openwall.com/lists/oss-security/2020/05/19/2Mailing List, Third Party Advisory
https://en.blog.nic.cz/2020/05/19/nxnsattack-upgrade-resolvers-to-stop-new-kind-of-random-subdomain-attack/Technical Description, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2024/04/msg00017.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/76Y4FITMOH6RVPWAANGV7NB2ZHPJJGDQ/
https://www.knot-resolver.cz/2020-05-19-knot-resolver-5.1.1.htmlRelease Notes, Vendor Advisory

Timeline

Published: May 19, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-12667?

How severe is CVE-2020-12667?

CVE-2020-12667 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 2.62% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12667?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-12667?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST