From 144dfbc12c09333bb0c912c4678e2f518362a219 Mon Sep 17 00:00:00 2001
From: Viktor Liu <viktor@netbird.io>
Date: Mon, 25 May 2026 17:02:28 +0200
Subject: [PATCH] Capture listener locally in accept loops to avoid nil deref
 on Stop

---
 client/vnc/server/server.go         | 8 +++++++-
 client/vnc/server/server_darwin.go  | 8 +++++++-
 client/vnc/server/server_windows.go | 9 ++++++++-
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/client/vnc/server/server.go b/client/vnc/server/server.go
index d14584625..3ed69d909 100644
--- a/client/vnc/server/server.go
+++ b/client/vnc/server/server.go
@@ -682,8 +682,14 @@ func (s *Server) Stop() error {
 
 // acceptLoop handles VNC connections directly (user session mode).
 func (s *Server) acceptLoop() {
+	s.mu.Lock()
+	ln := s.listener
+	s.mu.Unlock()
+	if ln == nil {
+		return
+	}
 	for {
-		conn, err := s.listener.Accept()
+		conn, err := ln.Accept()
 		if err != nil {
 			select {
 			case <-s.ctx.Done():
diff --git a/client/vnc/server/server_darwin.go b/client/vnc/server/server_darwin.go
index 18b5bbb7b..593de3e79 100644
--- a/client/vnc/server/server_darwin.go
+++ b/client/vnc/server/server_darwin.go
@@ -30,8 +30,14 @@ func (s *Server) serviceAcceptLoop() {
 
 	log.Info("service mode, proxying connections to per-user agent over Unix socket")
 
+	s.mu.Lock()
+	ln := s.listener
+	s.mu.Unlock()
+	if ln == nil {
+		return
+	}
 	for {
-		conn, err := s.listener.Accept()
+		conn, err := ln.Accept()
 		if err != nil {
 			select {
 			case <-s.ctx.Done():
diff --git a/client/vnc/server/server_windows.go b/client/vnc/server/server_windows.go
index 0d13dc045..88ebf74f8 100644
--- a/client/vnc/server/server_windows.go
+++ b/client/vnc/server/server_windows.go
@@ -248,8 +248,15 @@ func (s *Server) serviceAcceptLoop() {
 
 	log.Info("service mode, proxying connections to agent over Unix socket")
 
+	s.mu.Lock()
+	ln := s.listener
+	s.mu.Unlock()
+	if ln == nil {
+		sm.Stop()
+		return
+	}
 	for {
-		conn, err := s.listener.Accept()
+		conn, err := ln.Accept()
 		if err != nil {
 			select {
 			case <-s.ctx.Done():