CVE-2021-26720

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    CVE-2021-26720

    Published: 17 Feb 2021Last Modified: 15 Mar 2026

    Summary:

    Details: 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.

    References: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796, 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.launchpad.net/ubuntu/+source/avahi/+bug/1870824, https://bugzilla.suse.com/show_bug.cgi?id=1180827

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: N/A

    Events:

    Introduced- None
    Fixed -None

    Affected versions

    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
    CVE-2021-26720 | CVE-DB