From 87a41cf558523b6b0f5d7102e976b33745ae77d7 Mon Sep 17 00:00:00 2001
From: Oleg Guba <oleg.guba@gmail.com>
Date: Thu, 5 Jun 2025 14:14:15 -0700
Subject: [PATCH] [plugin/cache] create a copy of a response to ensure original
 data is never modified

Signed-off-by: Oleg Guba <oleg.guba@gmail.com>
---
 plugin/cache/cache.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/plugin/cache/cache.go b/plugin/cache/cache.go
index 4a6377b9ad..6dc6dc0a21 100644
--- a/plugin/cache/cache.go
+++ b/plugin/cache/cache.go
@@ -182,6 +182,7 @@ func (w *ResponseWriter) RemoteAddr() net.Addr {
 
 // WriteMsg implements the dns.ResponseWriter interface.
 func (w *ResponseWriter) WriteMsg(res *dns.Msg) error {
+	res = res.Copy()
 	mt, _ := response.Typify(res, w.now().UTC())
 
 	// key returns empty string for anything we don't want to cache.