CVE-2020-12662

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 3.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-05-19 · updated 2026-06-17
Weakness: CWE-400

Description

Unbound before 1.10.1 has Insufficient Control of Network Message Volume, aka an "NXNSAttack" issue. This is triggered by random subdomains in the NSDNAME in NS records.

Affected products

Canonical Ubuntu Linux: 18.04, 19.10, 20.04
Debian Linux: 9.0, 10.0
Fedoraproject Fedora: 31, 32
NLnet Labs Unbound: before 1.10.1 — fixed in 1.10.1
openSUSE Leap: 15.1, 15.2

How to fix

Upgrade to a fixed version: NLnet Labs Unbound 1.10.1. Check the vendor advisory for mitigations.

References

http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00067.html
http://lists.opensuse.org/opensuse-security-announce/2020-06/msg00069.html
http://www.nxnsattack.com
http://www.openwall.com/lists/oss-security/2020/05/19/5
https://lists.debian.org/debian-lts-announce/2021/02/msg00017.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/F5NFROI2OMCZLYRTCNGHGO3TUD32LCIQ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YJ42N2HBZ3DXMSEC56SWIIOFQGOS5M7I/
https://nlnetlabs.nl/downloads/unbound/CVE-2020-12662_2020-12663.txt
https://security.FreeBSD.org/advisories/FreeBSD-SA-20:19.unbound.asc
https://security.netapp.com/advisory/ntap-20200702-0006/
https://usn.ubuntu.com/4374-1/
https://www.debian.org/security/2020/dsa-4694

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