{"id":"CLSA-2026-1787932412","summary":"Fix CVE(s): CVE-2021-26720","details":"   * SECURITY UPDATE: local symlink attack through the unicast .local DNS\n     check: /etc/network/if-up.d/avahi-daemon exec's\n     /usr/lib/avahi/avahi-daemon-check-dns.sh as root, and the script\n     writes into /run/avahi-daemon (the checked_nameservers[.$$] cache and\n     the disabled-for-unicast-local tag) without protecting against\n     symlinks, so a local attacker able to place symlinks in that\n     avahi-owned directory can make root create arbitrary empty files or\n     cause a denial of service.\n     - debian/avahi-daemon.if-up: run the check script under\n       \"sudo -u avahi -g avahi\" instead of exec'ing it as root, so the\n       writes are performed by the same unprivileged account that owns\n       /run/avahi-daemon. Backported verbatim from Debian stretch\n       0.6.32-2+deb9u1 (DLA-3047-1); the alternative vendor fix, dropping\n       the check-dns mechanism outright (Debian buster 0.7-4+deb10u1,\n       Ubuntu focal 0.7-4ubuntu7), is not applicable here because bionic\n       ships libnss-mdns 0.10-8ubuntu1, the same generation as stretch.\n     - debian/control: add sudo to the avahi-daemon Depends, required by\n       the privilege drop.\n     - CVE-2021-26720","modified":"2026-10-26T09:32:03.753629424Z","published":"2026-08-29T10:28:02Z","upstream":["CVE-2021-26720"],"references":[{"type":"ADVISORY","url":"https://errata.tuxcare.com/els_os/ubuntu18.04els/CLSA-2026-1787932412.html"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-26720"}],"affected":[{"package":{"name":"avahi-autoipd","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/avahi-autoipd?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"avahi-daemon","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/avahi-daemon?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"avahi-discover","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/avahi-discover?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"avahi-dnsconfd","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/avahi-dnsconfd?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"avahi-ui-utils","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/avahi-ui-utils?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"avahi-utils","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/avahi-utils?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"gir1.2-avahi-0.6","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/gir1.2-avahi-0.6?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-client-dev","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-client-dev?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-client3","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-client3?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-common-data","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-common-data?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-common-dev","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-common-dev?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-common3","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-common3?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-compat-libdnssd-dev","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-compat-libdnssd-dev?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-compat-libdnssd1","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-compat-libdnssd1?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-core-dev","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-core-dev?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-core7","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-core7?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-glib-dev","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-glib-dev?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-glib1","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-glib1?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-gobject-dev","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-gobject-dev?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-gobject0","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-gobject0?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-ui-gtk3-0","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-ui-gtk3-0?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"libavahi-ui-gtk3-dev","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/libavahi-ui-gtk3-dev?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}},{"package":{"name":"python-avahi","ecosystem":"TuxCare:Ubuntu:18.04","purl":"pkg:deb/tuxcare/python-avahi?distro=ubuntu-18.04"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.7-3.1ubuntu1.3+tuxcare.els1"}]}],"database_specific":{"source":"https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/ubuntu18.04els/CLSA-2026-1787932412.json"}}],"schema_version":"1.9.0"}