@@ -21,6 +21,7 @@ SRC_URI = "http://www.thekelleys.org.uk/dnsmasq/${@['archive/', ''][float(d.getV
file://CVE-2026-4893.patch \
file://CVE-2026-5172.patch \
file://CVE-2026-2291.patch \
+ file://CVE-2026-4890.patch \
"
SRC_URI[sha256sum] = "8f6666b542403b5ee7ccce66ea73a4a51cf19dd49392aaccd37231a2c51b303b"
new file mode 100644
@@ -0,0 +1,74 @@
+From 12e5ee3495842ededf8057758ef8da59745bbf33 Mon Sep 17 00:00:00 2001
+From: Simon Kelley <simon@thekelleys.org.uk>
+Date: Fri, 10 Apr 2026 22:16:45 +0100
+Subject: [PATCH] Fix NSEC bitmap parsing infinite loop. CVE-2026-4890
+
+Report from Royce M <royce@xchglabs.com>.
+
+Location: dnssec.c:1290-1306, dnssec.c:1450-1463
+
+The bitmap window iteration advances by p[1] instead of p[1]+2 (missing the 2-byte window header). With bitmap_length=0, both rdlen and p are
+unchanged, causing an infinite loop and dnsmasq stops responding to all queries.
+
+The same code accesses p[2] after only checking rdlen >= 2 without verifying p[1] >= 1, causing OOB reads at 6 locations.
+
+Both bugs are reachable before RRSIG validation (confirmed by the source comment at line 2125), so no valid DNSSEC signatures are needed.
+
+CVE: CVE-2026-4890
+Upstream-Status: Backport [https://sources.debian.org/src/dnsmasq/2.90-4~deb12u2/debian/patches/CVE-2026-4890.patch]
+
+Signed-off-by: Benjamin Robin <benjamin.robin@bootlin.com>
+---
+ src/dnssec.c | 14 +++++++-------
+ 1 file changed, 7 insertions(+), 7 deletions(-)
+
+diff --git a/src/dnssec.c b/src/dnssec.c
+index ed2f53ff..68f1b5d0 100644
+--- a/src/dnssec.c
++++ b/src/dnssec.c
+@@ -1270,10 +1270,10 @@ static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsi
+ packet checked to be as long as rdlen implies in prove_non_existence() */
+
+ /* If we can prove that there's no NS record, return that information. */
+- if (nons && rdlen >= 2 && p[0] == 0 && (p[2] & (0x80 >> T_NS)) != 0)
++ if (nons && rdlen >= 2 && p[0] == 0 && p[1] >= 1 && (p[2] & (0x80 >> T_NS)) != 0)
+ *nons = 0;
+
+- if (rdlen >= 2 && p[0] == 0)
++ if (rdlen >= 2 && p[0] == 0 && p[1] >= 1)
+ {
+ /* A CNAME answer would also be valid, so if there's a CNAME is should
+ have been returned. */
+@@ -1301,8 +1301,8 @@ static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsi
+ break; /* finished checking */
+ }
+
+- rdlen -= p[1];
+- p += p[1];
++ rdlen -= p[1] + 2;
++ p += p[1] + 2;
+ }
+
+ return 0;
+@@ -1429,7 +1429,7 @@ static int check_nsec3_coverage(struct dns_header *header, size_t plen, int dige
+ p += hash_len; /* skip next-domain hash */
+ rdlen -= p - psave;
+
+- if (rdlen >= 2 && p[0] == 0)
++ if (rdlen >= 2 && p[0] == 0 && p[1] >= 1)
+ {
+ /* If we can prove that there's no NS record, return that information. */
+ if (nons && (p[2] & (0x80 >> T_NS)) != 0)
+@@ -1458,8 +1458,8 @@ static int check_nsec3_coverage(struct dns_header *header, size_t plen, int dige
+ break; /* finished checking */
+ }
+
+- rdlen -= p[1];
+- p += p[1];
++ rdlen -= p[1] + 2;
++ p += p[1] + 2;
+ }
+
+ return 1;
+--
+2.43.0
A Denial of Service (DoS) vulnerability in the DNSSEC validation of dnsmasq allows remote attackers to cause a denial of service via a crafted DNS packet. This patch is used by debian bookworm (2.90-4_deb12u2). Signed-off-by: Benjamin Robin (Schneider Electric) <benjamin.robin@bootlin.com> --- This patch needs to be applied on top of the previous CVE-2026-2291 patch --- Changes in v2: - Fix email subject - Link to v1: https://patch.msgid.link/20260701-dnsmasq-cve-2026-4890-v1-1-9daafc81fde3@bootlin.com --- .../recipes-support/dnsmasq/dnsmasq_2.90.bb | 1 + .../dnsmasq/files/CVE-2026-4890.patch | 74 ++++++++++++++++++++++ 2 files changed, 75 insertions(+) --- base-commit: b0c2c648a1af89e7a8dd4c2ec841f3bc0ed0ccb9 change-id: 20260701-dnsmasq-cve-2026-4890-f5b3a76de3ad prerequisite-change-id: 20260701-dnsmasq-cve-2026-2291-fc2db33dde8d:v1 prerequisite-patch-id: e7e3fdcabd23649336d34bd2f492f09007d73472 Best regards, -- Benjamin Robin (Schneider Electric) <benjamin.robin@bootlin.com>