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Fencer Vulns
high 7.5

CVE-2020-8621 json

Attempting QNAME minimization after forwarding can lead to an assertion failure in resolver.c

published 2020-08-21 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-29469

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

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.

Patch / fix

  • ISC BIND9 9.16.6, 9.17.4
  • bind9 Debian 14, Debian 13, Debian 12 1:9.16.6-1

debian advisories DEBIAN-CVE-2020-8621

  • bind9 Ubuntu 20.04 LTS 1:9.16.1-0ubuntu2.3

ubuntu advisories UBUNTU-CVE-2020-8621

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • bind SLES for SAP 15, SLES 15-LTSS, SLE Module for Server Applications 15 SP2 +5 more 9.16.6-12.32.1
  • sysuser-tools SLES for SAP 15, SLES 15-LTSS, SLE Module for Development Tools 15 SP2 +4 more 2.0-4.2.8

suse advisories SUSE-SU-2020:2914-1

  • bind openSUSE Tumbleweed 9.16.20-1.4
  • bind openSUSE Leap 15.1 9.16.6-lp151.11.9.1
  • libuv openSUSE Leap 15.1 1.18.0-lp151.3.3.1
  • sysuser-tools openSUSE Leap 15.1 2.0-lp151.4.3.1
  • bind openSUSE Leap 15.2 9.16.6-lp152.14.3.1
  • libuv openSUSE Leap 15.2 1.18.0-lp152.4.3.1
  • sysuser-tools openSUSE Leap 15.2 2.0-lp152.5.3.1

opensuse advisories openSUSE-SU-2024:10650-1openSUSE-SU-2020:1701-1openSUSE-SU-2020:1699-1

  • bind Alpine 3.24, Alpine 3.23, Alpine 3.22 +12 more 9.16.6-r0

alpine advisories ALPINE-CVE-2020-8621

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-8621 updated cvss 7.5

bind: Attempting QNAME minimization after forwarding can lead to an assertion failure in resolver.c

  • Red Hat Enterprise Linux 5 bind, bind97 Red Hat Enterprise Linux 6 bind, bind-sdb, bind-libs, bind-utils, bind-chroot Red Hat Enterprise Linux 7 bind, bind-sdb, bind-libs, bind-utils, bind-chroot, bind-pkcs11, +6 more Red Hat Enterprise Linux 8 bind, bind-sdb, bind-libs, bind-utils, bind-chroot, bind-pkcs11, +7 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.06% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:N/A:P

Affected products

  • ISC BIND9

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.