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CVE-2022-3204

Published: 26 September 2022

A vulnerability named 'Non-Responsive Delegation Attack' (NRDelegation Attack) has been discovered in various DNS resolving software. The NRDelegation Attack works by having a malicious delegation with a considerable number of non responsive nameservers. The attack starts by querying a resolver for a record that relies on those unresponsive nameservers. The attack can cause a resolver to spend a lot of time/resources resolving records under a malicious delegation point where a considerable number of unresponsive NS records reside. It can trigger high CPU usage in some resolver implementations that continually look in the cache for resolved NS records in that delegation. This can lead to degraded performance and eventually denial of service in orchestrated attacks. Unbound does not suffer from high CPU usage, but resources are still needed for resolving the malicious delegation. Unbound will keep trying to resolve the record until hard limits are reached. Based on the nature of the attack and the replies, different limits could be reached. From version 1.16.3 on, Unbound introduces fixes for better performance when under load, by cutting opportunistic queries for nameserver discovery and DNSKEY prefetching and limiting the number of times a delegation point can issue a cache lookup for missing records.

Priority

Medium

Cvss 3 Severity Score

7.5

Score breakdown

Status

Package Release Status
unbound
Launchpad, Ubuntu, Debian
bionic
Released (1.6.7-1ubuntu2.6)
focal
Released (1.9.4-2ubuntu1.4)
jammy
Released (1.13.1-1ubuntu5.3)
trusty Needed

upstream
Released (1.16.3-1)
kinetic
Released (1.16.2-1ubuntu0.1)
lunar Not vulnerable
(1.17.0-1)
xenial Needed

mantic Not vulnerable
(1.17.0-1)
Patches:
upstream: https://github.com/NLnetLabs/unbound/commit/137719522a8ea5b380fbb6206d2466f402f5b554

Severity score breakdown

Parameter Value
Base score 7.5
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H