ELA-624-1 avahi security update

denial of service

Related CVEs CVE-2021-3468 CVE-2021-26720

It was discovered that the Debian package of Avahi, a framework for Multicast DNS Service Discovery, executed the script avahi-daemon-check-dns.sh with root privileges which would allow a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /var/run/avahi-daemon. This script is now executed with the privileges of user and group avahi and requires sudo in order to achieve that.

Furthermore it was found (CVE-2021-3468) that the event used to signal the termination of the client connection on the avahi Unix socket is not correctly handled in the client_work function, allowing a local attacker to trigger an infinite loop.

For Debian 8 jessie, these problems have been fixed in version 0.6.31-5+deb8u1.

We recommend that you upgrade your avahi packages.

Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/