oss-security - Unbound: disclosure of CVE-2023-50387 and CVE-2023-50868 DNSSEC validation vulnerabilities

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Date: Tue, 13 Feb 2024 15:07:38 +0100
From: Yorgos Thessalonikefs <yorgos@...etlabs.nl>
To: oss-security@...ts.openwall.com
Subject: Unbound: disclosure of CVE-2023-50387 and CVE-2023-50868 DNSSEC
 validation vulnerabilities

Hi there,

(The official announcement and more information can be found at:
https://nlnetlabs.nl/news/2024/Feb/13/unbound-1.19.1-released/)

DNSSEC protocol vulnerabilities have been discovered that render various
DNSSEC validators victims of Denial Of Service while trying to validate
specially crafted DNSSEC responses.

There are two known vulnerabilities: CVE-2023-50387 (referred here as
the KeyTrap vulnerability) and CVE-2023-50868 (referred here as the
NSEC3 vulnerability).

We are categorizing the vulnerabilities with a HIGH severity for
Unbound.
We are releasing 1.19.1 on the 13th of February including the relevant
fixes.

== Summary
Both vulnerabilities, via specially crafted DNSSEC answers, can lead
DNSSEC validators down a very CPU intensive and time costly
validation/NSEC3 hash calculation path.
This results in degraded performance and denial of service in trivially
orchestrated attacks.

Unbound 1.19.1 includes fixes for better performance under such DNSSEC
validation attacks.

== Affected products
Unbound up to and including 1.19.0.

== Solution
Install Unbound 1.19.1.
Or apply the following patch to the latest Unbound versions (1.18.0 - 
1.19.0):
https://nlnetlabs.nl/downloads/unbound/patch_CVE-2023-50387_CVE-2023-50868.diff

Apply the patch using:

     patch -p1 < patch_CVE-2023-50387_CVE-2023-50868.diff

== Acknowledgments
We would like to thank Elias Heftrig, Haya Schulmann, Niklas Vogel, and 
Michael Waidner from the German National Research Center for Applied 
Cybersecurity ATHENE for discovering and responsibly disclosing the 
KeyTrap vulnerability.
We would like to thank Petr Špaček from ISC for discovering and
responsibly disclosing the NSEC3 vulnerability.

* This email is signed. Keys of the NLnet Labs people are published on
https://www.nlnetlabs.nl/people/ *

Best regards,
-- Yorgos

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