From 2285db2b629e400a37e7a741ccf07ae8388ed1e9 Mon Sep 17 00:00:00 2001
From: Viktor Liu <viktor@netbird.io>
Date: Tue, 19 May 2026 13:08:47 +0200
Subject: [PATCH] Treat ExtendedClipboard messages with the Caps bit as Caps
 regardless of co-set action bits

---
 client/vnc/server/session_clipboard.go | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/client/vnc/server/session_clipboard.go b/client/vnc/server/session_clipboard.go
index 3b3e13abe..c4554970f 100644
--- a/client/vnc/server/session_clipboard.go
+++ b/client/vnc/server/session_clipboard.go
@@ -139,11 +139,16 @@ func (s *session) handleExtCutText(payloadLen uint32) error {
 	formats := flags & extClipFormatMask
 	rest := buf[4:]
 
-	switch action {
-	case extClipActionCaps:
+	// A Caps message sets the Caps bit alongside one bit per action the
+	// peer supports, so the action byte is multi-bit. Detect it first; the
+	// remaining actions are single-bit and are dispatched after.
+	if action&extClipActionCaps != 0 {
 		// Client max sizes are informational for us today: we only emit
 		// text and already cap it at extClipMaxText.
 		return nil
+	}
+
+	switch action {
 	case extClipActionRequest:
 		if formats&extClipFormatText != 0 {
 			return s.sendExtClipProvideText()