Debian Security Advisory

DLA-3047-1 avahi -- LTS security update

Date Reported:
07 Jun 2022
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 984938.
In Mitre's CVE dictionary: CVE-2021-3468, CVE-2021-26720.
More information:

It was discovered that the Debian package of Avahi, a framework for Multicast DNS Service Discovery, executed the script 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.

The aforementioned script has been removed from Debian 10 Buster onwards. The workaround could not be implemented for Debian 9 Stretch because libnss-mdns 0.10 does not provide the required functionality to replace it.

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 9 stretch, these problems have been fixed in version 0.6.32-2+deb9u1.

We recommend that you upgrade your avahi packages.

For the detailed security status of avahi please refer to its security tracker page at:

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: