CVE-2021-26720

NameCVE-2021-26720
Descriptionavahi-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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDLA-3047-1, ELA-624-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
avahi (PTS)jessie, jessie (lts)0.6.31-5+deb8u2fixed
stretch (security)0.6.32-2+deb9u1fixed
stretch (lts), stretch0.6.32-2+deb9u2fixed
buster (security), buster, buster (lts)0.7-4+deb10u3fixed
bullseye0.8-5+deb11u2fixed
bookworm0.8-10fixed
sid, trixie0.8-13fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
avahisourcejessie0.6.31-5+deb8u1ELA-624-1
avahisourcestretch0.6.32-2+deb9u1DLA-3047-1
avahisourcebuster0.7-4+deb10u1
avahisource(unstable)0.8-4

Notes

https://www.openwall.com/lists/oss-security/2021/02/15/2
Fixed by removing the avahi-daemon-check-dns.sh script.
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