Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In 0.9-rc2 and earlier, avahi-daemon can be crashed by sending unsolicited announcements containing CNAME resource records pointing it to resource records with short TTLs. As soon as they expire avahi-daemon crashes.
CVSS Score
6.5
EPSS Score
0.0
Published
2026-01-12
Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In 0.9-rc2 and earlier, avahi-daemon can be crashed by sending 2 unsolicited announcements with CNAME resource records 2 seconds apart.
CVSS Score
6.5
EPSS Score
0.0
Published
2026-01-12
Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In 0.9-rc2 and earlier, an unprivileged local users can crash avahi-daemon (with wide-area disabled) by creating record browsers with the AVAHI_LOOKUP_USE_WIDE_AREA flag set via D-Bus. This can be done by either calling
the RecordBrowserNew method directly or creating hostname/address/service resolvers/browsers that create those browsers internally themselves.
CVSS Score
5.5
EPSS Score
0.0
Published
2026-01-12
Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In versions up to and including 0.9-rc2, the simple protocol server ignores the documented client limit and accepts unlimited connections, allowing for easy local DoS. Although `CLIENTS_MAX` is defined, `server_work()` unconditionally `accept()`s and `client_new()` always appends the new client and increments `n_clients`. There is no check against the limit. When client cannot be accepted as a result of maximal socket number of avahi-daemon, it logs unconditionally error per each connection. Unprivileged local users can exhaust daemon memory and file descriptors, causing a denial of service system-wide for mDNS/DNS-SD. Exhausting local file descriptors causes increased system load caused by logging errors of each of request. Overloading prevents glibc calls using nss-mdns plugins to resolve `*.local.` names and link-local addresses. As of time of publication, no known patched versions are available, but a candidate fix is available in pull request 808, and some workarounds are available. Simple clients are offered for nss-mdns package functionality. It is not possible to disable the unix socket `/run/avahi-daemon/socket`, but resolution requests received via DBus are not affected directly. Tools avahi-resolve, avahi-resolve-address and avahi-resolve-host-name are not affected, they use DBus interface. It is possible to change permissions of unix socket after avahi-daemon is started. But avahi-daemon does not provide any configuration for it. Additional access restrictions like SELinux can also prevent unwanted tools to access the socket and keep resolution working for trusted users.
CVSS Score
5.5
EPSS Score
0.0
Published
2025-12-18
A vulnerability was found in Avahi. A reachable assertion exists in the avahi_alternative_host_name() function.
CVSS Score
6.2
EPSS Score
0.0
Published
2023-11-02
A vulnerability was found in Avahi, where a reachable assertion exists in avahi_dns_packet_append_record.
CVSS Score
6.2
EPSS Score
0.0
Published
2023-11-02
A vulnerability was found in Avahi. A reachable assertion exists in the avahi_escape_label() function.
CVSS Score
6.2
EPSS Score
0.0
Published
2023-11-02
A vulnerability was found in Avahi. A reachable assertion exists in the dbus_set_host_name function.
CVSS Score
6.2
EPSS Score
0.0
Published
2023-11-02
A vulnerability was found in Avahi. A reachable assertion exists in the avahi_rdata_parse() function.
CVSS Score
6.2
EPSS Score
0.0
Published
2023-11-02
A flaw was found in avahi in versions 0.6 up to 0.8. 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. The highest threat from this vulnerability is to the availability of the avahi service, which becomes unresponsive after this flaw is triggered.
CVSS Score
5.5
EPSS Score
0.0
Published
2021-06-02
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