Description
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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | avahi | 0.8-4 | — |
| Debian 13 | avahi | 0.8-4 | — |
| Debian 12 | avahi | 0.8-4 | — |
| Debian 9 | avahi | 0.6.32-2+deb9u1 | DLA-3047-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 18.04 LTS | avahi | No fix yet | — |
| Ubuntu Pro 16.04 LTS | avahi | No fix yet | — |
| Ubuntu Pro 14.04 LTS | avahi | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP2 | avahi +1 | 0.7-3.6.1 | SUSE-SU-2021:0551-1 |
| SLES 15 | avahi +1 | 0.6.32-5.13.1 | SUSE-SU-2021:1845-1 |
| SLES 12 SP5 | avahi | 0.6.32-32.12.2 | SUSE-SU-2021:0563-1 |
| SLES 12 SP5 | avahi-glib2 | 0.6.32-32.12.3 | SUSE-SU-2021:0563-1 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 | avahi +1 | 0.6.32-5.13.1 | SUSE-SU-2021:1845-1 |
| SLES for SAP 12 SP5 | avahi | 0.6.32-32.12.2 | SUSE-SU-2021:0563-1 |
| SLES for SAP 12 SP5 | avahi-glib2 | 0.6.32-32.12.3 | SUSE-SU-2021:0563-1 |
| SLE HPC 15 | avahi +1 | 0.6.32-5.13.1 | SUSE-SU-2021:1845-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | avahi | 0.8-7.2 | openSUSE-SU-2024:10643-1 |
| openSUSE Leap 15.3 | avahi +1 | 0.6.32-5.13.1 | openSUSE-SU-2021:1845-1 |
| openSUSE Leap 15.2 | avahi +3 | 0.7-lp152.3.6.1 | openSUSE-SU-2021:0370-1 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | avahi | 0.8-1 | — |
| Azure Linux 2 (CBL-Mariner) | avahi | 0.8-1 | — |
Advisories 7
- DLA-3047-1 avahi - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2021:0551-1 Security update for avahi SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:1845-1 Security update for avahi SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10643-1 avahi-0.8-7.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:0563-1 Security update for avahi SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0370-1 Security update for avahi SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:1845-1 Security update for avahi SUSE / openSUSE Security Updates · May 7, 2025
References
- https://packages.debian.org/buster/avahi-daemon
- https://packages.debian.org/sid/avahi-daemon
- https://packages.debian.org/bullseye/avahi-daemon
- https://security-tracker.debian.org/tracker/CVE-2021-26720
- https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824
- https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog
- https://www.openwall.com/lists/oss-security/2021/02/15/2
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796
- https://bugzilla.suse.com/show_bug.cgi?id=1180827
- [debian-lts-announce] 20220607 [SECURITY] [DLA 3047-1] avahi security update mailing-list