CVE-2021-26720 json
avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon, and allows a…
published 2021-02-17 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-13508
- cvss
- 7.8
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 33%
- public exploits
- 0
- none known
Summary
avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon, and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE), not the upstream Avahi product.
Patch / fix
- avahi Debian 14, Debian 13, Debian 12 0.8-4
debian advisories DEBIAN-CVE-2021-26720
- avahi SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 0.6.32-5.13.1
- avahi-glib2 SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 0.6.32-5.13.1
- avahi SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 0.6.32-32.12.2
- avahi-glib2 SLES for SAP 12 SP5, SLES 12 SP5, SLE Workstation Extension 12 SP5 +1 more 0.6.32-32.12.3
- avahi SLE Module for Package Hub 15 SP2, SLE Module for Desktop Applications 15 SP2, SLE Module for Basesystem 15 SP2 0.7-3.6.1
- avahi-glib2 SLE Module for Desktop Applications 15 SP2, SLE Module for Basesystem 15 SP2 0.7-3.6.1
suse advisories SUSE-SU-2021:1845-1SUSE-SU-2021:0563-1SUSE-SU-2021:0551-1
- avahi openSUSE Tumbleweed 0.8-7.2
- avahi openSUSE Leap 15.3 0.6.32-5.13.1
- avahi-glib2 openSUSE Leap 15.3 0.6.32-5.13.1
- avahi openSUSE Leap 15.2 0.7-lp152.3.6.1
- avahi-qt4 openSUSE Leap 15.2 0.7-lp152.3.6.1
- avahi-mono openSUSE Leap 15.2 0.7-lp152.3.6.1
- avahi-glib2 openSUSE Leap 15.2 0.7-lp152.3.6.1
opensuse advisories openSUSE-SU-2024:10643-1openSUSE-SU-2021:1845-1openSUSE-SU-2021:0370-1
- avahi CBL-Mariner 2.0, Azure Linux 3.0 0.8-1
azure linux advisories AZL-34547AZL-6323
Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT
Exploit prediction
0.40% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVD | 2.0 | 4.6 | AV:L/AC:L/Au:N/C:P/I:P/A:P |
Classification
- Weakness
-
- CWE-59 Improper Link Resolution Before File Access
References
-
packages.debian.org
/buster/avahi-daemon
product, third-party-advisory
-
packages.debian.org
/sid/avahi-daemon
product, third-party-advisory
-
packages.debian.org
/bullseye/avahi-daemon
product, third-party-advisory
-
security-tracker.debian.org
/tracker/CVE-2021-26720
third-party-advisory
-
bugs.launchpad.net
/ubuntu/+source/avahi/+bug/1870824
issue-tracking, third-party-advisory
-
metadata.ftp-master.debian.org
/changelogs/main/a/avahi/avahi_0.8-4_changelog
broken-link, third-party-advisory
-
openwall.com
/lists/oss-security/2021/02/15/2
mailing-list, third-party-advisory
-
bugs.debian.org
/cgi-bin/bugreport.cgi?bug=982796
mailing-list, third-party-advisory
-
bugzilla.suse.com
/show_bug.cgi?id=1180827
issue-tracking, third-party-advisory
-
lists.debian.org
/debian-lts-announce/2022/06/msg00009.html
mailing-list, third-party-advisory
Sources
- CVE List CVE-2021-26720
- NVD CVE-2021-26720
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.