Resource exhaustion in Knot Resolver - CVE-2020-12667
Published: June 25, 2020
Vulnerability identifier: #VU29248
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2020-12667
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to application does not properly control consumption of internal resources when processing NSDNAME in NS records. A remote attacker can perform traffic amplification via a crafted DNS answer from an attacker-controlled server. This vulnerability is dubbed "NXNSAttack".
Affected software
Knot Resolver
knot-resolver (Alpine package)
knot-resolver (Ubuntu package)
knot-resolver
Fedora
Ubuntu
knot-resolver (Alpine package)
knot-resolver (Ubuntu package)
knot-resolver
Fedora
Ubuntu
How to mitigate CVE-2020-12667
Install updates from vendor's website.
Knot Resolver - update to 5.1.1
knot-resolver (Alpine package) - update to 4.3.0-r3
knot-resolver (Ubuntu package) - update to 3.2.1-3ubuntu2.2
knot-resolver - addressed in versions 5.1.1-1.el7, 5.1.1-1.el8, 5.1.1-1.fc30, 5.1.1-1.fc31, 5.1.1-1.fc32, 5.1.2-1.fc31, 5.1.3-1.fc31
knot-resolver (Alpine package) - update to 4.3.0-r3
knot-resolver (Ubuntu package) - update to 3.2.1-3ubuntu2.2
knot-resolver - addressed in versions 5.1.1-1.el7, 5.1.1-1.el8, 5.1.1-1.fc30, 5.1.1-1.fc31, 5.1.1-1.fc32, 5.1.2-1.fc31, 5.1.3-1.fc31
External References
- http://cyber-security-group.cs.tau.ac.il/#
- http://www.openwall.com/lists/oss-security/2020/05/19/2
- https://en.blog.nic.cz/2020/05/19/nxnsattack-upgrade-resolvers-to-stop-new-kind-of-random-subdomain-attack/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/76Y4FITMOH6RVPWAANGV7NB2ZHPJJGDQ/
- https://www.knot-resolver.cz/2020-05-19-knot-resolver-5.1.1.html
Related Security Bulletins
- DNS amplification attack in Knot Resolver
- Resource exhaustion in knot-resolver (Alpine package)
- Ubuntu update for knot-resolver
- Fedora 32 update for knot-resolver
- Fedora EPEL 8 update for knot-resolver
- Fedora EPEL 7 update for knot-resolver
- Fedora 31 update for knot-resolver
- Fedora 30 update for knot-resolver
- Fedora 31 update for knot-resolver
- Fedora 31 update for knot-resolver