From d5d18ced67e969d6a5052cacdbd7d4b2c97a1a3f Mon Sep 17 00:00:00 2001 From: Evgeny Vereshchagin Date: Wed, 17 Dec 2025 08:11:23 +0000 Subject: [PATCH] core: refuse to create wide-area record browsers when wide-area is off It fixes a bug where it was possible for unprivileged local users to crash avahi-daemon (with wide-area disabled) by creating record browsers with the AVAHI_LOOKUP_USE_WIDE_AREA flag set via D-Bus (either by calling the RecordBrowserNew method directly or by creating hostname/address/service resolvers/browsers that create those browsers internally themselves). ``` $ gdbus call --system --dest org.freedesktop.Avahi --object-path / --method org.freedesktop.Avahi.Server.ResolveHostName -- -1 -1 yo.local -1 1 Error: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying ``` ``` dbus-protocol.c: interface=org.freedesktop.Avahi.Server, path=/, member=ResolveHostName avahi-daemon: wide-area.c:725: avahi_wide_area_scan_cache: Assertion `e' failed. ==307948== ==307948== Process terminating with default action of signal 6 (SIGABRT) ==307948== at 0x4B3630C: __pthread_kill_implementation (pthread_kill.c:44) ==307948== by 0x4ADF921: raise (raise.c:26) ==307948== by 0x4AC74AB: abort (abort.c:77) ==307948== by 0x4AC741F: __assert_fail_base.cold (assert.c:118) ==307948== by 0x48D8B85: avahi_wide_area_scan_cache (wide-area.c:725) ==307948== by 0x48C8953: lookup_scan_cache (browse.c:351) ==307948== by 0x48C8B1B: lookup_go (browse.c:386) ==307948== by 0x48C9148: defer_callback (browse.c:516) ==307948== by 0x48AEA0E: expiration_event (timeeventq.c:94) ==307948== by 0x489D3AE: timeout_callback (simple-watch.c:447) ==307948== by 0x489D787: avahi_simple_poll_dispatch (simple-watch.c:563) ==307948== by 0x489D91E: avahi_simple_poll_iterate (simple-watch.c:605) ==307948== ``` wide-area has been disabled by default since 9c4214146738146e454f098264690e8e884c39bd (v0.9-rc2). https://github.com/avahi/avahi/security/advisories/GHSA-mhf3-865v-g5rc CVE: CVE-2025-68276 Upstream-Status: Backport [https://github.com/avahi/avahi/pull/806/commits/0c013e2e819be3bda74cecf48b5f64956cf8a760] Signed-off-by: Adarsh Jagadish Kamini --- avahi-core/browse.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/avahi-core/browse.c b/avahi-core/browse.c index e8a915e..59d53cb 100644 --- a/avahi-core/browse.c +++ b/avahi-core/browse.c @@ -541,6 +541,11 @@ AvahiSRecordBrowser *avahi_s_record_browser_prepare( AVAHI_CHECK_VALIDITY_RETURN_NULL(server, AVAHI_FLAGS_VALID(flags, AVAHI_LOOKUP_USE_WIDE_AREA|AVAHI_LOOKUP_USE_MULTICAST), AVAHI_ERR_INVALID_FLAGS); AVAHI_CHECK_VALIDITY_RETURN_NULL(server, !(flags & AVAHI_LOOKUP_USE_WIDE_AREA) || !(flags & AVAHI_LOOKUP_USE_MULTICAST), AVAHI_ERR_INVALID_FLAGS); + if ((flags & AVAHI_LOOKUP_USE_WIDE_AREA) && !server->wide_area_lookup_engine) { + avahi_server_set_errno(server, AVAHI_ERR_NOT_SUPPORTED); + return NULL; + } + if (!(b = avahi_new(AvahiSRecordBrowser, 1))) { avahi_server_set_errno(server, AVAHI_ERR_NO_MEMORY); return NULL; -- 2.34.1