From 2e5d219205ebec64a66bfd29bba73dd5049c434f Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Sat, 4 Apr 2026 18:10:31 +0200
Subject: [PATCH] sendf: fix CR detection if no LF is in the chunk

When doing line ending conversions, and a chunk contains no '\n', the
function returned early without updating prev_cr to reflect the last
byte. It could then lead to CRLFs sequences not get converted when
occuring right on the boundary border.

Found by Codex Security

Closes #21221
---
 lib/sendf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/sendf.c b/lib/sendf.c
index ab67da26ca..74e7038a7f 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -1009,6 +1009,8 @@ static CURLcode cr_lc_read(struct Curl_easy *data,
 
     if(!nread || !memchr(buf, '\n', nread)) {
       /* nothing to convert, return this right away */
+      if(nread)
+        ctx->prev_cr = (buf[nread - 1] == '\r');
       if(ctx->read_eos)
         ctx->eos = TRUE;
       *pnread = nread;