CVE-2020-8621 Attempting QNAME minimization after forwarding can lead to an assertion failure in resolver.c

What is CVE-2020-8621?

CVE-2020-8621 is a high-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 21 Aug 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In BIND 9.14.0 -> 9.16.5, 9.17.0 -> 9.17.3, If a server is configured with both QNAME minimization and 'forward first' then an attacker who can send queries to it may be able to trigger the condition that will cause the server to crash. Servers that 'forward only' are not affected.

Weakness: CWE-617

Which versions are affected by CVE-2020-8621?

It affects 5 products.

Products include Canonical Ubuntu Linux, Isc Bind, Netapp Steelstore Cloud Integrated Storage, Opensuse Leap, Synology Dns Server.

How do I fix CVE-2020-8621?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2020-8621 being exploited?

There is no known exploitation of CVE-2020-8621 in the wild and no public exploit code.

Other vulnerabilities in Canonical Ubuntu Linux

• CVE-2020-11651 SaltStack Salt Authentication Bypass Exploited Critical 9.8
• CVE-2020-7247 OpenSMTPD Remote Code Execution Exploited Critical 9.8
• CVE-2019-16928 Exim Out-of-bounds Write Exploited Critical 9.8
• CVE-2018-6789 Exim Buffer Overflow Exploited Critical 9.8
• CVE-2015-2590 Oracle Java SE and Java SE Embedded Remote Code Execution Exploited Critical 9.8

All Canonical Ubuntu Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2020-8621, DEBIAN-CVE-2020-8621, GHSA-7vc6-qmjj-2j83, UBUNTU-CVE-2020-8621.