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Fix CVE-2026-10846: Query reply spoofing

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(patch was taken from the z-stream)

Resolves: RHEL-210699
This commit is contained in:
Fedor Vorobev 2026-08-04 11:21:10 +02:00
parent 7d700cdb56
commit d847601ec7
2 changed files with 207 additions and 1 deletions
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200
ldns-1.7.1-CVE-2026-10846.patch Normal file
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@ -0,0 +1,200 @@
From 734e9e1fa9bd115ca416dcfde53ff199c390f01d Mon Sep 17 00:00:00 2001
From: RHEL Packaging Agent <redhat-ymir-agent@redhat.com>
Date: Fri, 17 Jul 2026 09:26:15 +0000
Subject: [PATCH] Fix CVE-2026-10846: Add address/port/TXID and question
matching checks
Backport of the official NLnet Labs patch for CVE-2026-10846 to ldns 1.7.1.
This adds verification of the reply source address and port, transaction ID
matching, qdcount validation, and question section matching to prevent
DNS response spoofing attacks.
---
ldns-1.7.1_python3/error.c | 6 +++
ldns-1.7.1_python3/ldns/error.h | 5 +-
ldns-1.7.1_python3/net.c | 92 ++++++++++++++++++++++++++++++++-
3 files changed, 100 insertions(+), 3 deletions(-)
diff --git a/ldns-1.7.1_python3/error.c b/ldns-1.7.1_python3/error.c
index 7943017..6874f6b 100644
--- a/ldns-1.7.1_python3/error.c
+++ b/ldns-1.7.1_python3/error.c
@@ -157,6 +157,12 @@ ldns_lookup_table ldns_error_str[] = {
"X509_STORE_CTX_set0_dane() functions within OpenSSL >= 1.1.0 "
"to be able to verify the DANE-TA usage type." },
#endif
+ { LDNS_STATUS_ID_DID_NOT_MATCH,
+ "Response ID did not match the query ID" },
+ { LDNS_STATUS_QDCOUNT_MUST_BE_ONE,
+ "The query section MUST contain exactly one question" },
+ { LDNS_STATUS_QUERY_DID_NOT_MATCH,
+ "The question in the response did not match the query" },
{ 0, NULL }
};
diff --git a/ldns-1.7.1_python3/ldns/error.h b/ldns-1.7.1_python3/ldns/error.h
index 15f49a2..936df38 100644
--- a/ldns-1.7.1_python3/ldns/error.h
+++ b/ldns-1.7.1_python3/ldns/error.h
@@ -129,7 +129,10 @@ enum ldns_enum_status {
LDNS_STATUS_RDATA_OVERFLOW,
LDNS_STATUS_SYNTAX_SUPERFLUOUS_TEXT_ERR,
LDNS_STATUS_NSEC3_DOMAINNAME_OVERFLOW,
- LDNS_STATUS_DANE_NEED_OPENSSL_GE_1_1_FOR_DANE_TA
+ LDNS_STATUS_DANE_NEED_OPENSSL_GE_1_1_FOR_DANE_TA,
+ LDNS_STATUS_ID_DID_NOT_MATCH,
+ LDNS_STATUS_QDCOUNT_MUST_BE_ONE,
+ LDNS_STATUS_QUERY_DID_NOT_MATCH
};
typedef enum ldns_enum_status ldns_status;
diff --git a/ldns-1.7.1_python3/net.c b/ldns-1.7.1_python3/net.c
index 38d00cf..e075757 100644
--- a/ldns-1.7.1_python3/net.c
+++ b/ldns-1.7.1_python3/net.c
@@ -441,6 +441,50 @@ ldns_udp_bgsend2(ldns_buffer *qbin,
return ldns_udp_bgsend_from(qbin, to, tolen, NULL, 0, timeout);
}
+/** helper sockaddr compare function. returns -1, 0 or 1. */
+static int
+ldns_sockaddr_cmp(const struct sockaddr_storage* addr1, socklen_t len1,
+ const struct sockaddr_storage* addr2, socklen_t len2)
+{
+ struct sockaddr_in* p1_in = (struct sockaddr_in*)addr1;
+ struct sockaddr_in* p2_in = (struct sockaddr_in*)addr2;
+ struct sockaddr_in6* p1_in6 = (struct sockaddr_in6*)addr1;
+ struct sockaddr_in6* p2_in6 = (struct sockaddr_in6*)addr2;
+ if(len1 < len2)
+ return -1;
+ if(len1 > len2)
+ return 1;
+ assert(len1 == len2);
+ if( p1_in->sin_family < p2_in->sin_family)
+ return -1;
+ if( p1_in->sin_family > p2_in->sin_family)
+ return 1;
+ assert( p1_in->sin_family == p2_in->sin_family );
+ /* compare ip4 */
+ if( p1_in->sin_family == AF_INET ) {
+ /* just order it, ntohs not required */
+ if(p1_in->sin_port < p2_in->sin_port)
+ return -1;
+ if(p1_in->sin_port > p2_in->sin_port)
+ return 1;
+ assert(p1_in->sin_port == p2_in->sin_port);
+ return memcmp(&p1_in->sin_addr, &p2_in->sin_addr,
+ sizeof(p1_in->sin_addr));
+ } else if (p1_in6->sin6_family == AF_INET6) {
+ /* just order it, ntohs not required */
+ if(p1_in6->sin6_port < p2_in6->sin6_port)
+ return -1;
+ if(p1_in6->sin6_port > p2_in6->sin6_port)
+ return 1;
+ assert(p1_in6->sin6_port == p2_in6->sin6_port);
+ return memcmp(&p1_in6->sin6_addr, &p2_in6->sin6_addr,
+ sizeof(p1_in6->sin6_addr));
+ } else {
+ /* eek unknown type, perform this comparison for sanity. */
+ return memcmp(addr1, addr2, len1);
+ }
+}
+
static ldns_status
ldns_udp_send_from(uint8_t **result, ldns_buffer *qbin,
const struct sockaddr_storage *to , socklen_t tolen,
@@ -449,6 +493,8 @@ ldns_udp_send_from(uint8_t **result, ldns_buffer *qbin,
{
int sockfd;
uint8_t *answer;
+ struct sockaddr_storage reply_addr;
+ socklen_t reply_addr_len;
sockfd = ldns_udp_bgsend_from(qbin, to, tolen, from, fromlen, timeout);
@@ -467,13 +513,21 @@ ldns_udp_send_from(uint8_t **result, ldns_buffer *qbin,
* but returns a 'NETWORK_ERROR' much like a timeout. */
ldns_sock_nonblock(sockfd);
- answer = ldns_udp_read_wire(sockfd, answer_size, NULL, NULL);
+ reply_addr_len = sizeof(reply_addr);
+ memset(&reply_addr, 0, reply_addr_len);
+ answer = ldns_udp_read_wire(sockfd, answer_size, &reply_addr,
+ &reply_addr_len);
close_socket(sockfd);
if (!answer) {
/* oops */
return LDNS_STATUS_NETWORK_ERR;
}
+ /* Check that the reply came from the to addr. */
+ if(ldns_sockaddr_cmp(to, tolen, &reply_addr, reply_addr_len) != 0) {
+ free(answer);
+ return LDNS_STATUS_NETWORK_ERR;
+ }
*result = answer;
return LDNS_STATUS_OK;
@@ -512,6 +566,10 @@ ldns_send_buffer(ldns_pkt **result, ldns_resolver *r, ldns_buffer *qb, ldns_rdf
assert(r != NULL);
+ /* The query should at least have one question */
+ if(ldns_buffer_limit(qb) < 6 || ldns_buffer_read_u16_at(qb, 4) != 1)
+ return LDNS_STATUS_QDCOUNT_MUST_BE_ONE;
+
status = LDNS_STATUS_OK;
rtt = ldns_resolver_rtt(r);
ns_array = ldns_resolver_nameservers(r);
@@ -599,6 +657,16 @@ ldns_send_buffer(ldns_pkt **result, ldns_resolver *r, ldns_buffer *qb, ldns_rdf
ldns_resolver_set_nameserver_rtt(r, i, LDNS_RESOLV_RTT_INF);
status = send_status;
}
+ if(reply_bytes && ldns_buffer_limit(qb) >= 2) {
+ uint16_t txid = ldns_buffer_read_u16_at(qb, 0);
+ if(reply_size < 2 ||
+ ldns_read_uint16(reply_bytes) != txid) {
+ status = LDNS_STATUS_ID_DID_NOT_MATCH;
+ LDNS_FREE(reply_bytes);
+ reply_bytes = NULL;
+ reply_size = 0;
+ }
+ }
/* obey the fail directive */
if (!reply_bytes) {
@@ -608,7 +676,7 @@ ldns_send_buffer(ldns_pkt **result, ldns_resolver *r, ldns_buffer *qb, ldns_rdf
LDNS_FREE(src);
}
LDNS_FREE(ns);
- return LDNS_STATUS_ERR;
+ return status ? status : LDNS_STATUS_ERR;
} else {
LDNS_FREE(ns);
continue;
@@ -670,6 +738,26 @@ ldns_send_buffer(ldns_pkt **result, ldns_resolver *r, ldns_buffer *qb, ldns_rdf
#endif /* HAVE_SSL */
LDNS_FREE(reply_bytes);
+ if (reply) {
+ ldns_pkt *query = NULL;
+
+ if(ldns_pkt_qdcount(reply) != 1) {
+ status = LDNS_STATUS_QDCOUNT_MUST_BE_ONE;
+ ldns_pkt_free(reply);
+ reply = NULL;
+
+ } else if(ldns_wire2pkt(&query
+ , ldns_buffer_begin(qb)
+ , ldns_buffer_position(qb)) != LDNS_STATUS_OK
+ || ldns_pkt_qdcount(query) != 1
+ || ldns_rr_compare(ldns_rr_list_rr(ldns_pkt_question(query),0)
+ ,ldns_rr_list_rr(ldns_pkt_question(reply),0))){
+ status = LDNS_STATUS_QUERY_DID_NOT_MATCH;
+ ldns_pkt_free(reply);
+ reply = NULL;
+ }
+ ldns_pkt_free(query);
+ }
if (result) {
*result = reply;
}

8
ldns.spec
View File

@ -39,7 +39,7 @@
Summary: Low-level DNS(SEC) library with API
Name: ldns
Version: 1.7.1
Release: 12%{?dist}
Release: 13%{?dist}
License: BSD
Url: https://www.nlnetlabs.nl/%{name}/
@ -57,6 +57,8 @@ Patch3: ldns-1.7.1-out-of-boud-read-vuln.patch
Patch4: ldns-1.7.1-Support-sysconfig-python-module-in-python_devel.patch
# https://github.com/NLnetLabs/ldns/commit/a5a5dd867fdb934a7ce3637dd9def598f0979247
Patch5: ldns-1.7.1-Use-PYTHON_LIBS-instead-of-PYTHON_LDFLAGS.patch
# https://nlnetlabs.nl/downloads/ldns/patch_cve_2026-10846.diff
Patch6: ldns-1.7.1-CVE-2026-10846.patch
# Only needed for builds from svn snapshot
@ -359,6 +361,10 @@ rm -rf doc/man
%doc doc
%changelog
* Tue Aug 04 2026 Fedor Vorobev <fvorobev@redhat.com> - 1.7.1-13
- Fix CVE-2026-10846: Off-path poisoning attacks due to insufficient
query-response matching (RHEL-210699)
* Tue Dec 03 2024 Petr Menšík <pemensik@redhat.com> - 1.7.1-12
- Fix digest calculation of sha256 (RHEL-20391)