knot-resolver before version 4.3.0 is vulnerable to denial of service through high CPU utilization. DNS replies with very many resource records might be processed very inefficiently, in extreme cases taking even several CPU seconds for each such uncached message. For example, a few thousand A records can be squashed into one DNS message (limit is 64kB).

The remote Ubuntu 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-7047-1 advisory.

    Vladimr unt discovered that Knot Resolver incorrectly handled input during DNSSEC validation. A     remote attacker could possibly use this issue to bypass certain validations. (CVE-2019-10190)

    Vladimr unt discovered that Knot Resolver incorrectly handled input during DNSSEC validation. A     remote attacker could possibly use this issue to downgrade DNSSEC-secure domains to a DNSSEC-insecure     state, resulting

    in a domain hijacking attack. (CVE-2019-10191)

    Vladimr unt discovered that Knot Resolver incorrectly handled certain

    DNS replies with many resource records. An attacker could possibly use

    this issue to consume system resources, resulting in a denial of service. (CVE-2019-19331)

    Lior Shafir, Yehuda Afek, and Anat Bremler-Barr discovered that Knot Resolver incorrectly handled certain     queries. A remote attacker could

    use this issue to perform an amplification attack directed at a target. (CVE-2020-12667)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-3795 advisory.

  - A vulnerability was discovered in DNS resolver component of knot resolver through version 3.2.0 before     4.1.0 which allows remote attackers to bypass DNSSEC validation for non-existence answer. NXDOMAIN answer     would get passed through to the client even if its DNSSEC validation failed, instead of sending a SERVFAIL     packet. Caching is not affected by this particular bug but see CVE-2019-10191. (CVE-2019-10190)

  - A vulnerability was discovered in DNS resolver of knot resolver before version 4.1.0 which allows remote     attackers to downgrade DNSSEC-secure domains to DNSSEC-insecure state, opening possibility of domain     hijack using attacks against insecure DNS protocol. (CVE-2019-10191)

  - knot-resolver before version 4.3.0 is vulnerable to denial of service through high CPU utilization. DNS     replies with very many resource records might be processed very inefficiently, in extreme cases taking     even several CPU seconds for each such uncached message. For example, a few thousand A records can be     squashed into one DNS message (limit is 64kB). (CVE-2019-19331)

  - 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. (CVE-2020-12667)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

- update to upstream version 4.3.0

  - fixes CVE-2019-19331

  - root.keys is moved to /var/lib/knot-resolver -     knot-resolver no longer requires write permission to     /etc/knot-resolver/

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Severity
207977	Ubuntu 20.04 LTS : Knot Resolver vulnerabilities (USN-7047-1)	Nessus	Ubuntu Local Security Checks	high
193916	Debian dla-3795 : knot-resolver - security update	Nessus	Debian Local Security Checks	high
132029	Fedora 31 : knot-resolver (2019-866dc03603)	Nessus	Fedora Local Security Checks	high
132028	Fedora 30 : knot-resolver (2019-44ccfa9b29)	Nessus	Fedora Local Security Checks	high

Detections

Analytics

CVE-2019-19331

high

Tenable Plugins

high

high

high

high