Reachable assertion in avahi_escape_label

A vulnerability was found in Avahi. A reachable assertion exists in the avahi_escape_label() function.

Avahi: simple protocol server ignores accepts unlimited connections and logs failures without limit

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-rc5, 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.

Avahi has Uncontrolled Recursion in lookup_handle_cname function

Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In versions 0.9rc2 and below, avahi-daemon can be crashed via a segmentation fault by sending an unsolicited mDNS response containing a recursive CNAME record, where the alias and canonical name point to the same domain (e.g., "h.local" as a CNAME for "h.local"). This causes unbounded recursion in the lookup_handle_cname function, leading to stack exhaustion. The vulnerability affects record browsers where AVAHI_LOOKUP_USE_MULTICAST is set explicitly, which includes record browsers created by resolvers used by nss-mdns. This issue is patched in commit 78eab31128479f06e30beb8c1cbf99dd921e2524, which is part of version 0.9-rc3.

The consume_labels function in avahi-core/dns.c in Avahi before 0.6.16 allows remote attackers to cause a denial of service (infinite loop) via a crafted compressed DNS response with a label that points to itself.

avahi: assert fail local DoS via D-Bus

The Avahi daemon in Avahi before 0.6.20 allows attackers to cause a denial of service (exit) via empty TXT data over D-Bus, which triggers an assert error.

avahi: avahi-daemon DoS (application abort) via packet with source port 0

The originates_from_local_legacy_unicast_socket function (avahi-core/server.c) in avahi-daemon in Avahi before 0.6.24 allows remote attackers to cause a denial of service (crash) via a crafted mDNS packet with a source port of 0, which triggers an assertion failure.

avahi: remote DoS via legacy unicast mDNS queries

The originates_from_local_legacy_unicast_socket function in avahi-core/server.c in avahi-daemon 0.6.23 does not account for the network byte order of a port number when processing incoming multicast packets, which allows remote attackers to cause a denial of service (network bandwidth and CPU consumption) via a crafted legacy unicast mDNS query packet that triggers a multicast packet storm.

Avahi before 0.6.15 does not verify the sender identity of netlink messages to ensure that they come from the kernel instead of another process, which allows local users to spoof network changes to Avahi.

Buffer overflow in avahi-core in Avahi before 0.6.10 allows local users to execute arbitrary code via unknown vectors.

Avahi before 0.6.10 allows local users to cause a denial of service (mDNS/DNS-SD service disconnect) via unspecified mDNS name conflicts.

Avahi: Reachable assertion in `transport_flags_from_domain()` via conflicting publish flags crashes avahi-daemon

Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. Prior to version 0.9-rc4, any unprivileged local user can crash avahi-daemon by sending a single D-Bus method call with conflicting publish flags. This issue has been patched in version 0.9-rc4.

Avahi has a reachable assertion in lookup_start

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.

Avahi has a reachable assertion in lookup_multicast_callback

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.

Avahi has a reachable assertion in avahi_wide_area_scan_cache

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.

avahi: Multicast DNS responds to unicast queries outside of local network

avahi-daemon in Avahi through 0.6.32 and 0.7 inadvertently responds to IPv6 unicast queries with source addresses that are not on-link, which allows remote attackers to cause a denial of service (traffic amplification) and may cause information leakage by obtaining potentially sensitive information from the responding device via port-5353 UDP packets. NOTE: this may overlap CVE-2015-2809.

Reachable assertion in avahi_alternative_host_name

A vulnerability was found in Avahi. A reachable assertion exists in the avahi_alternative_host_name() function.

Reachable assertion in avahi_rdata_parse

A vulnerability was found in Avahi. A reachable assertion exists in the avahi_rdata_parse() function.

Reachable assertion in dbus_set_host_name

A vulnerability was found in Avahi. A reachable assertion exists in the dbus_set_host_name function.

Reachable assertion in avahi_dns_packet_append_record

A vulnerability was found in Avahi, where a reachable assertion exists in avahi_dns_packet_append_record.

avahi: avahi-daemon can be crashed via DBus

A vulnerability was found in the avahi library. This flaw allows an unprivileged user to make a dbus call, causing the avahi daemon to crash.