dnsmasq: Fix CVE-2026-4893

Pick patch from [1] dnsmasq 2.90 debian bookworm pacthes.

[1] https://sources.debian.org/src/dnsmasq/2.90-4~deb12u2/debian/patches/CVE-2026-4893.patch

Signed-off-by: Hugo SIMELIERE (Schneider Electric) <hsimeliere.opensource@witekio.com>
Reviewed-by: Bruno VERNAY <bruno.vernay@se.com>
Signed-off-by: Anuj Mittal <anuj.mittal@oss.qualcomm.com>

2 files changed, 39 insertions, 0 deletions

diff --git a/meta-networking/recipes-support/dnsmasq/dnsmasq_2.90.bb b/meta-networking/recipes-support/dnsmasq/dnsmasq_2.90.bb
index 21411839c7..4e548f6e59 100644
--- a/meta-networking/recipes-support/dnsmasq/dnsmasq_2.90.bb
+++ b/meta-networking/recipes-support/dnsmasq/dnsmasq_2.90.bb
@@ -18,6 +18,7 @@ SRC_URI = "http://www.thekelleys.org.uk/dnsmasq/${@['archive/', ''][float(d.getV
            file://dnsmasq-resolved.conf \
            file://CVE-2026-4891.patch \
            file://CVE-2026-4892.patch \
+           file://CVE-2026-4893.patch \
 "
 SRC_URI[sha256sum] = "8f6666b542403b5ee7ccce66ea73a4a51cf19dd49392aaccd37231a2c51b303b"
 
diff --git a/meta-networking/recipes-support/dnsmasq/files/CVE-2026-4893.patch b/meta-networking/recipes-support/dnsmasq/files/CVE-2026-4893.patch
new file mode 100644
index 0000000000..8aea321329
--- /dev/null
+++ b/meta-networking/recipes-support/dnsmasq/files/CVE-2026-4893.patch
@@ -0,0 +1,38 @@
+From 262aadd7a38947d2299234c8c9cf736ff6ad955d Mon Sep 17 00:00:00 2001
+From: Simon Kelley <simon@thekelleys.org.uk>
+Date: Wed, 25 Mar 2026 23:22:37 +0000
+Subject: [PATCH] Fix broken client subnet validation. CVE-2026-4893
+
+Bug report from Royce M <royce@xchglabs.com>
+
+Location: forward.c:713, edns0.c:421
+
+With --add-subnet enabled, process_reply() passes the OPT record
+length (~23 bytes) instead of the packet length to check_source().
+All internal bounds checks fail, and the function always returns 1.
+ECS source validation per RFC 7871 Section 9.2 is completely bypassed.
+
+CVE: CVE-2026-4893
+Upstream-Status: Backport [https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=e3a26d092e47bf1d18aeadb758e4ca35c83b5f2d]
+
+Signed-off-by: Hugo SIMELIERE (Schneider Electric) <hsimeliere.opensource@witekio.com>
+---
+ src/forward.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/forward.c b/src/forward.c
+index 32f37e40..19ff4401 100644
+--- a/src/forward.c
++++ b/src/forward.c
+@@ -710,7 +710,7 @@ static size_t process_reply(struct dns_header *header, time_t now, struct server
+       /* Get extended RCODE. */
+       rcode |= sizep[2] << 4;
+ 
+-      if (option_bool(OPT_CLIENT_SUBNET) && !check_source(header, plen, pheader, query_source))
++      if (option_bool(OPT_CLIENT_SUBNET) && !check_source(header, n, pheader, query_source))
+        {
+          my_syslog(LOG_WARNING, _("discarding DNS reply: subnet option mismatch"));
+          return 0;
+-- 
+2.43.0
+