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dnsmasq: apply six CVE-fix upstream patches to 2.90

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Apply upstream patches for the recently published CVEs in dnsmasq.

Source: https://thekelleys.org.uk/dnsmasq/CVE/
Reference: https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2026q2/018471.html

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
Link: https://github.com/openwrt/openwrt/pull/23328
(cherry picked from commit dc04999b1ff41d6bac64c484e62502f933c32852)
[added this to main branch first, 002-CVE-2026-4890.dnsmasq-2.91.patch modified]
Link: https://github.com/openwrt/openwrt/pull/23365
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
This commit is contained in:
Hannu Nyman 2026-05-12 22:56:36 +03:00 committed by Hauke Mehrtens
parent 766cbba1de
commit 15250e11aa
7 changed files with 205 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
package/network/services/dnsmasq/Makefile
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@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
PKG_NAME:=dnsmasq
PKG_UPSTREAM_VERSION:=2.90
PKG_VERSION:=$(subst test,~~test,$(subst rc,~rc,$(PKG_UPSTREAM_VERSION)))
PKG_RELEASE:=4
PKG_RELEASE:=5
PKG_SOURCE:=$(PKG_NAME)-$(PKG_UPSTREAM_VERSION).tar.xz
PKG_SOURCE_URL:=https://thekelleys.org.uk/dnsmasq/

29
package/network/services/dnsmasq/patches/001-CVE-2026-2291.patch Normal file
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@ -0,0 +1,29 @@
commit ec2fbfbbdaa7d7db1c707dce26ce1a37cfe09660
Author: Simon Kelley <simon@thekelleys.org.uk>
Date: Fri Apr 10 16:29:31 2026 +0100
Fix buffer overflow in struct bigname. CVE-2026-2291
All buffers capable of holding a domain name should be
at least MAXDNAME*2 + 1 bytes long, where MAXDNAME is the maximum
size of a domain name. The accounts for the trailing zero and the
fact that some characters are escaped in the internal representation
of a domain name in dnsmasq.
The declaration of struct bigname get this wrong, with the effect
that a remote attacker capable of asking DNS queries or answering DNS
queries can cause a large OOB write in the heap.
This was first spotted by Andrew S. Fasano.
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -467,7 +467,7 @@ struct interface_name {
};
union bigname {
- char name[MAXDNAME];
+ char name[(2*MAXDNAME) + 1];
union bigname *next; /* freelist */
};

63
package/network/services/dnsmasq/patches/002-CVE-2026-4890.dnsmasq-2.91.patch Normal file
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@ -0,0 +1,63 @@
commit de76f21e115c451cf0653790fc4b209cd4778a07
Author: Simon Kelley <simon@thekelleys.org.uk>
Date: Fri Apr 10 22:16:45 2026 +0100
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.
--- a/src/dnssec.c
+++ b/src/dnssec.c
@@ -1270,10 +1270,10 @@ static int prove_non_existence_nsec(stru
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(stru
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 d
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 d
break; /* finished checking */
}
- rdlen -= p[1];
- p += p[1];
+ rdlen -= p[1] + 2;
+ p += p[1] + 2;
}
return 1;

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package/network/services/dnsmasq/patches/003-CVE-2026-4891.patch Normal file
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@ -0,0 +1,32 @@
commit 2cacea42e4d45717bd0ce3ccfe8e78960245e5da
Author: Simon Kelley <simon@thekelleys.org.uk>
Date: Wed Mar 25 23:04:08 2026 +0000
Verify rdlen field in RRSIG packets. CVE-2026-4891
Bug report from Royce M <royce@xchglabs.com>
This avoids crafted packets which give a value for rdlen _less_
then the space taken up by the fixed data and the signer's name
and engender a negative calculated length for the signature.
--- a/src/dnssec.c
+++ b/src/dnssec.c
@@ -546,10 +546,14 @@ static int validate_rrset(time_t now, st
*ttl_out = ttl;
}
-
+
+ /* Don't trust rdlen not to be too small and give us a negative sig_len
+ It has already been checked that it doesn't run us off the end
+ of the packet. */
+ if ((sig_len = rdlen - (p - psav)) <= 0)
+ return STAT_BOGUS;
+
sig = p;
- sig_len = rdlen - (p - psav);
-
nsigttl = htonl(orig_ttl);
hash->update(ctx, 18, psav);

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package/network/services/dnsmasq/patches/004-CVE-2026-4892.patch Normal file
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@ -0,0 +1,28 @@
commit 011a36c51438c986535a7248ed2e7f424f8e1078
Author: Simon Kelley <simon@thekelleys.org.uk>
Date: Wed Mar 25 23:16:35 2026 +0000
Fix buffer overflow in helper.c with large CLIDs. CVE-2026-4892
Bug reported bt Royce M <royce@xchglabs.com>
Location: helper.c:265-270
DHCPv6 CLIDs can be up to 65535 bytes. When --dhcp-script is configured,
the helper hex-encodes raw CLID bytes via sprintf("%.2x") into daemon->packet (5131 bytes).
A 1000-byte CLID writes ~3000 bytes. The helper process retains root privileges.
Note: log6_packet() correctly caps CLID to 100 bytes for logging, but the helper code path was missed.
--- a/src/helper.c
+++ b/src/helper.c
@@ -261,8 +261,8 @@ int create_helper(int event_fd, int err_
data.hostname_len + data.ed_len + data.clid_len, 1))
continue;
- /* CLID into packet */
- for (p = daemon->packet, i = 0; i < data.clid_len; i++)
+ /* CLID into packet: limit to 100 bytes to avoid overflowing buffer. */
+ for (p = daemon->packet, i = 0; i < data.clid_len && i < 100; i++)
{
p += sprintf(p, "%.2x", buf[i]);
if (i != data.clid_len - 1)

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package/network/services/dnsmasq/patches/005-CVE-2026-4893.patch Normal file
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@ -0,0 +1,26 @@
commit 434d68f2eb1a58744470698483a3ae09b5a9a870
Author: Simon Kelley <simon@thekelleys.org.uk>
Date: Wed Mar 25 23:22:37 2026 +0000
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.
--- a/src/forward.c
+++ b/src/forward.c
@@ -710,7 +710,7 @@ static size_t process_reply(struct dns_h
/* 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;

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package/network/services/dnsmasq/patches/006-CVE-2026-5172.patch Normal file
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@ -0,0 +1,26 @@
commit fa3c8ddef6712b52f562813317e6a997e1210123
Author: Simon Kelley <simon@thekelleys.org.uk>
Date: Mon Mar 30 16:24:33 2026 +0100
Fix buffer overflow vulnerability in extract_addresses() CVE-2026-5172
Thanks to Hugo Martinez Ray for spotting this.
The value of rdlen for an RR can be a lie, allowing the
call to extract_name() at rfc1025.c:952 to advance the value of p1
past the calculated end of the record. The makes the calculation
of bytes remaining in the RR underflow to a huge number and results
in a massive heap OOB read and certain crash.
--- a/src/rfc1035.c
+++ b/src/rfc1035.c
@@ -932,7 +932,8 @@ int extract_addresses(struct dns_header
/* Name, extract it then re-encode. */
int len;
- if (!extract_name(header, qlen, &p1, name, 1, 0))
+ /* rdlen may lie, and extract_name() advances p1 past where it says the record ends. */
+ if (!extract_name(header, qlen, &p1, name, 1, 0) || (p1 > endrr))
{
blockdata_free(addr.rrblock.rrdata);
return 2;