From 04cc27460ea15943873de6dac4983e52e3645756 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Thu, 6 May 2021 09:35:18 +0200
Subject: [PATCH] http: reset the header buffer when sending the request

A reused transfer handle could otherwise reuse the previous leftover
buffer and havoc would ensue.

Reported-by: sergio-nsk on github
Fixes #7018
Closes #7021
---
 lib/http.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/http.c b/lib/http.c
index b42d37efa..eece05513 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -3120,6 +3120,10 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
   /* initialize a dynamic send-buffer */
   Curl_dyn_init(&req, DYN_HTTP_REQUEST);
 
+  /* make sure the header buffer is reset - if there are leftovers from a
+     previous transfer */
+  Curl_dyn_reset(&data->state.headerb);
+
   /* add the main request stuff */
   /* GET/HEAD/POST/PUT */
   result = Curl_dyn_addf(&req, "%s ", request);