CVE-2021-26720

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.

• CWE-59

• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796Mailing List, Third Party Advisory
• https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824Issue Tracking, Third Party Advisory
• https://bugzilla.suse.com/show_bug.cgi?id=1180827Issue Tracking, Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2022/06/msg00009.htmlMailing List, Third Party Advisory
• https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelogBroken Link, Third Party Advisory
• https://packages.debian.org/bullseye/avahi-daemonProduct, Third Party Advisory
• https://packages.debian.org/buster/avahi-daemonProduct, Third Party Advisory
• https://packages.debian.org/sid/avahi-daemonProduct, Third Party Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-26720Third Party Advisory
• https://www.openwall.com/lists/oss-security/2021/02/15/2Mailing List, Third Party Advisory
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796Mailing List, Third Party Advisory
• https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824Issue Tracking, Third Party Advisory
• https://bugzilla.suse.com/show_bug.cgi?id=1180827Issue Tracking, Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2022/06/msg00009.htmlMailing List, Third Party Advisory
• https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelogBroken Link, Third Party Advisory
• https://packages.debian.org/bullseye/avahi-daemonProduct, Third Party Advisory
• https://packages.debian.org/buster/avahi-daemonProduct, Third Party Advisory
• https://packages.debian.org/sid/avahi-daemonProduct, Third Party Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-26720Third Party Advisory
• https://www.openwall.com/lists/oss-security/2021/02/15/2Mailing List, Third Party Advisory

Published

Feb 17, 2021

Last Modified

Jun 17, 2026

Status

Modified

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