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    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.

    Published:Feb 17, 2021
    Last Modified:Nov 21, 2024
    EPS:Feb 17, 2021
    EPSS Score:0.00034
    CVSS Score:7.8

    Affected Products

    Vendor
    Avahi
    Product
    Avahi
    Vendor
    Debian
    Product
    Debian Linux

    Exploits

    No exploit reference

    Related CVEs

    CVE-2026-34933 (CVSS 5.5) — Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. P…
    CVE-2026-24401 (CVSS 6.5) — Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. I…
    CVE-2025-68471 (CVSS 6.5) — Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. I…
    CVE-2025-68468 (CVSS 6.5) — Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. I…
    CVE-2025-68276 (CVSS 5.5) — Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. I…
    CVE-2025-59529 (CVSS 5.5) — Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. I…
    CVE-2023-38471 (CVSS 6.2) — A vulnerability was found in Avahi. A reachable assertion exists in the dbus_set_host_name function.…
    CVE-2023-38472 (CVSS 6.2) — A vulnerability was found in Avahi. A reachable assertion exists in the avahi_rdata_parse() function.…
    CVE-2023-38469 (CVSS 6.2) — A vulnerability was found in Avahi, where a reachable assertion exists in avahi_dns_packet_append_record.…
    CVE-2023-38470 (CVSS 6.2) — A vulnerability was found in Avahi. A reachable assertion exists in the avahi_escape_label() function.…

    References

    https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796
    https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824
    https://bugzilla.suse.com/show_bug.cgi?id=1180827
    https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html
    https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog
    https://packages.debian.org/bullseye/avahi-daemon
    https://packages.debian.org/buster/avahi-daemon
    https://packages.debian.org/sid/avahi-daemon
    https://security-tracker.debian.org/tracker/CVE-2021-26720
    https://www.openwall.com/lists/oss-security/2021/02/15/2
    https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796
    https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824
    https://bugzilla.suse.com/show_bug.cgi?id=1180827
    https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html
    https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog
    https://packages.debian.org/bullseye/avahi-daemon
    https://packages.debian.org/buster/avahi-daemon
    https://packages.debian.org/sid/avahi-daemon
    https://security-tracker.debian.org/tracker/CVE-2021-26720
    https://www.openwall.com/lists/oss-security/2021/02/15/2

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High