CVE-2020-8621: Attempting QNAME minimization after forwarding can lead to an assertion failure in resolver.c
First published: Fri Aug 21 2020(Updated: )
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.
Credit: security-officer@isc.org
| Affected Software | Affected Version | How to fix |
|---|---|---|
| debian/bind9 | 1:9.16.50-1~deb11u2 1:9.16.50-1~deb11u3 1:9.18.28-1~deb12u2 1:9.18.33-1~deb12u2 1:9.20.4-4 1:9.20.5-1 | |
| ISC BIND 9 | >=9.14.0<=9.16.5 | |
| ISC BIND 9 | >=9.17.0<=9.17.3 | |
| SUSE Linux | =15.1 | |
| SUSE Linux | =15.2 | |
| Ubuntu | =16.04 | |
| Ubuntu | =18.04 | |
| Ubuntu | =20.04 | |
| Synology DNS Server | <2.2.2-5027 | |
| NetApp SteelStore Cloud Integrated Storage |
Remedy
Upgrade to the patched release most closely related to your current version of BIND: BIND 9.16.6 BIND 9.17.4
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Reference Links
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00041.html
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00044.html
- https://kb.isc.org/docs/cve-2020-8621
- https://security.gentoo.org/glsa/202008-19
- https://security.netapp.com/advisory/ntap-20200827-0003/
- https://usn.ubuntu.com/4468-1/
- https://www.synology.com/security/advisory/Synology_SA_20_19
- https://launchpad.net/bugs/cve/CVE-2020-8621
- https://gitlab.isc.org/isc-projects/bind9/commit/81514ff925dfc6e0c293745e0fc8320a8af95586
- https://security-tracker.debian.org/tracker/CVE-2020-8621
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-8621
- https://nvd.nist.gov/vuln/detail/CVE-2020-8621
- https://ubuntu.com/security/CVE-2020-8621
Frequently Asked Questions
What is the severity of CVE-2020-8621?
The severity of CVE-2020-8621 is high with a severity value of 7.5.
Which versions of BIND are affected by CVE-2020-8621?
BIND versions 9.14.0 to 9.16.5 and 9.17.0 to 9.17.3 are affected by CVE-2020-8621.
How can an attacker exploit CVE-2020-8621?
An attacker can exploit CVE-2020-8621 by sending queries to a BIND server configured with both QNAME minimization and 'forward first', causing the server to crash.
Are servers configured with 'forward only' affected by CVE-2020-8621?
No, servers configured with 'forward only' are not affected by CVE-2020-8621.
How can I fix CVE-2020-8621?
To fix CVE-2020-8621, update your BIND server to a version that includes the fix for the vulnerability.
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