From b4b81deed9930fdb59cfbf8179218621c812497b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Fri, 20 Feb 2026 09:46:32 +0100
Subject: [PATCH] Fix stack Use-After-Return in SIG(0) handling

The asynchronous SIG(0) handling improperly used srcaddr, and dstaddr
from the caller's stack and didn't attach to aclenv.  This could
possibly lead to ACL bypass as an invalid srcaddr could be matched or
possible assertion failure if the ACL environment would change between
the initial call and the SIG(0) processing due to the server
reconfiguration.  This has been fixed.
---
 bin/named/server.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/bin/named/server.c b/bin/named/server.c
index 25eb888e7a..6a9a39846d 100644
--- a/bin/named/server.c
+++ b/bin/named/server.c
@@ -24,6 +24,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <dns/acl.h>
+
 #ifdef HAVE_DNSTAP
 #include <fstrm.h>
 #endif
@@ -280,10 +282,10 @@ struct zonelistentry {
  * asynchronously.
  */
 typedef struct matching_view_ctx {
-	isc_netaddr_t *srcaddr;
-	isc_netaddr_t *destaddr;
+	isc_netaddr_t srcaddr;
+	isc_netaddr_t destaddr;
 	dns_message_t *message;
-	dns_aclenv_t *env;
+	dns_aclenv_t *aclenv;
 	ns_server_t *sctx;
 	isc_loop_t *loop;
 	isc_job_cb cb;
@@ -9299,6 +9301,8 @@ get_matching_view_done(void *cbarg) {
 
 	mvctx->cb(mvctx->cbarg);
 
+	dns_aclenv_detach(&mvctx->aclenv);
+
 	if (mvctx->quota_result == ISC_R_SUCCESS) {
 		isc_quota_release(&mvctx->sctx->sig0checksquota);
 	}
@@ -9340,10 +9344,10 @@ get_matching_view_continue(void *cbarg, isc_result_t result) {
 		tsig = dns_tsigkey_identity(mvctx->message->tsigkey);
 	}
 
-	if (dns_acl_allowed(mvctx->srcaddr, tsig, mvctx->view->matchclients,
-			    mvctx->env) &&
-	    dns_acl_allowed(mvctx->destaddr, tsig,
-			    mvctx->view->matchdestinations, mvctx->env) &&
+	if (dns_acl_allowed(&mvctx->srcaddr, tsig, mvctx->view->matchclients,
+			    mvctx->aclenv) &&
+	    dns_acl_allowed(&mvctx->destaddr, tsig,
+			    mvctx->view->matchdestinations, mvctx->aclenv) &&
 	    !(mvctx->view->matchrecursiveonly &&
 	      (mvctx->message->flags & DNS_MESSAGEFLAG_RD) == 0))
 	{
@@ -9415,9 +9419,9 @@ get_matching_view(isc_netaddr_t *srcaddr, isc_netaddr_t *destaddr,
 
 	matching_view_ctx_t *mvctx = isc_mem_get(message->mctx, sizeof(*mvctx));
 	*mvctx = (matching_view_ctx_t){
-		.srcaddr = srcaddr,
-		.destaddr = destaddr,
-		.env = env,
+		.srcaddr = *srcaddr,
+		.destaddr = *destaddr,
+		.aclenv = dns_aclenv_ref(env),
 		.cb = cb,
 		.cbarg = cbarg,
 		.sigresult = sigresult,