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Please note that the fix for CVE-2024-52615 introduces CVE-2025-59529 which is not fixed yet (https://github.com/avahi/avahi/pull/808). You can mitigate this vulnerability by setting the `enable-wide-area=no` option. Patch `0011-properly-randomize-query-id-of-DNS-packets.patch` modify `configure.ac` and then `AVAHI_AUTORECONF` is set. This commit fixes the following vulnerabilities: - CVE-2021-3468: 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. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2021-3468 -447affe299- CVE-2023-38469: A vulnerability was found in Avahi, where a reachable assertion exists in avahi_dns_packet_append_record. https://www.cve.org/CVERecord?id=CVE-2023-38469 - CVE-2023-38470: A vulnerability was found in Avahi. A reachable assertion exists in the avahi_escape_label() function. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2023-38470 -a337a1ba7d- CVE-2023-38471: A vulnerability was found in Avahi. A reachable assertion exists in the dbus_set_host_name function. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2023-38471 - github.com/avahi/avahi/commit/894f085f402e023a98cbb6f5a3d117bd88d93b09 - CVE-2023-38472: A vulnerability was found in Avahi. A reachable assertion exists in the avahi_rdata_parse() function. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2023-38472 -b024ae5749- CVE-2023-38473: A vulnerability was found in Avahi. A reachable assertion exists in the avahi_alternative_host_name() function. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2023-38473 -b448c9f771- CVE-2024-52615: A flaw was found in Avahi-daemon, which relies on fixed source ports for wide-area DNS queries. This issue simplifies attacks where malicious DNS responses are injected. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2024-52615 -4e2e1ea090- https://github.com/avahi/avahi/issues/810 (introduce regression CVE-2025-59529) - CVE-2024-52616: A flaw was found in the Avahi-daemon, where it initializes DNS transaction IDs randomly only once at startup, incrementing them sequentially after that. This predictable behavior facilitates DNS spoofing attacks, allowing attackers to guess transaction IDs. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2024-52616 -f8710bdc8b- CVE-2025-68276: 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. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2025-68276 -2d48e42d44- CVE-2025-68468: 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. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2025-68468 -f66be13d7f- CVE-2025-68471: 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. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2025-68471 -9c6eb53bf2- CVE-2026-24401: 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. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2026-24401 -78eab31128Signed-off-by: Thomas Perale <thomas.perale@mind.be> Signed-off-by: Julien Olivain <ju.o@free.fr>
74 lines
2.3 KiB
Diff
74 lines
2.3 KiB
Diff
From 78eab31128479f06e30beb8c1cbf99dd921e2524 Mon Sep 17 00:00:00 2001
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From: Hugo Muis <198191869+friendlyhugo@users.noreply.github.com>
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Date: Sun, 2 Mar 2025 18:06:24 +0100
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Subject: [PATCH] core: fix uncontrolled recursion bug using a simple loop
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detection algorithm
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Closes https://github.com/avahi/avahi/issues/501
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CVE: CVE-2026-24401
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Upstream: https://github.com/avahi/avahi/commit/78eab31128479f06e30beb8c1cbf99dd921e2524
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Signed-off-by: Thomas Perale <thomas.perale@mind.be>
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---
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avahi-core/browse.c | 40 ++++++++++++++++++++++++++++++++++++++++
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1 file changed, 40 insertions(+)
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diff --git a/avahi-core/browse.c b/avahi-core/browse.c
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index ad08bd65f..e00cbed84 100644
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--- a/avahi-core/browse.c
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+++ b/avahi-core/browse.c
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@@ -401,6 +401,40 @@ static int lookup_go(AvahiSRBLookup *l) {
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return n;
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}
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+static int lookup_exists_in_path(AvahiSRBLookup* lookup, AvahiSRBLookup* from, AvahiSRBLookup* to) {
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+ AvahiRList* rl;
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+ if (from == to)
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+ return 0;
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+ for (rl = from->cname_lookups; rl; rl = rl->rlist_next) {
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+ int r = lookup_exists_in_path(lookup, rl->data, to);
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+ if (r == 1) {
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+ /* loop detected, propagate result */
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+ return r;
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+ } else if (r == 0) {
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+ /* is loop detected? */
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+ return lookup == from;
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+ } else {
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+ /* `to` not found, continue */
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+ continue;
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+ }
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+ }
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+ /* no path found */
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+ return -1;
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+}
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+
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+static int cname_would_create_loop(AvahiSRBLookup* l, AvahiSRBLookup* n) {
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+ int ret;
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+ if (l == n)
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+ /* Loop to self */
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+ return 1;
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+
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+ ret = lookup_exists_in_path(n, l->record_browser->root_lookup, l);
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+
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+ /* Path to n always exists */
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+ assert(ret != -1);
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+ return ret;
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+}
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+
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static void lookup_handle_cname(AvahiSRBLookup *l, AvahiIfIndex interface, AvahiProtocol protocol, AvahiLookupFlags flags, AvahiRecord *r) {
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AvahiKey *k;
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AvahiSRBLookup *n;
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@@ -420,6 +454,12 @@ static void lookup_handle_cname(AvahiSRBLookup *l, AvahiIfIndex interface, Avahi
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return;
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}
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+ if (cname_would_create_loop(l, n)) {
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+ /* CNAME loops are not allowed */
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+ lookup_unref(n);
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+ return;
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+ }
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+
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l->cname_lookups = avahi_rlist_prepend(l->cname_lookups, lookup_ref(n));
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lookup_go(n);
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