curl: fix CVE-2026-5773 - wrong reuse of SMB connection

libcurl's SMB handler marks connections for reuse (connkeep) without
verifying that subsequent requests target the same share. This allows
a second SMB request to the same host to reuse a connection
authenticated for a different share, potentially accessing data
without proper authorization.

The upstream fix removes connection reuse for SMB entirely in
lib/protocol.c, a file introduced in curl 8.20.0. For 8.7.1, the
equivalent fix is changing connkeep() to connclose() in lib/smb.c,
which prevents the connection from being returned to the pool.

Tested with SMBv1 server (Docker dperson/samba):
  Without patch: "Re-using existing connection" for different shares
  With patch: New connection per request, no reuse

Binary verified: Curl_conncontrol arg changes from 0 (KEEP) to 1 (CLOSE)

Reference: https://curl.se/docs/CVE-2026-5773.html

(From OE-Core rev: 7736f905e78162ac657d7a1c790dfa5701dd6b19)

Signed-off-by: Jaipaul Cheernam <jaipaul.cheernam@est.tech>
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>

meta/recipes-support/curl/curl/CVE-2026-5773.patch

@@ -0,0 +1,40 @@
+From 74a169575d6412dc0ff532acdf94de35a6c2a571 Mon Sep 17 00:00:00 2001
+From: Daniel Stenberg <daniel@haxx.se>
+Date: Sun, 5 Apr 2026 18:23:35 +0200
+Subject: [PATCH] protocol: disable connection reuse for SMB(S)
+
+Connections should only be reused when using the same "share" (and
+perhaps some additional conditions), but instead of fixing this flaw,
+this change completely disables connection reuse for SMB. This protocol
+is about to get dropped soon anyway.
+
+Reported-by: Osama Hamad
+Closes #21238
+
+CVE: CVE-2026-5773
+Upstream-Status: Backport [https://github.com/curl/curl/commit/74a169575d6412dc0ff532acdf94de35a6c2a571]
+
+Note: The upstream fix targets lib/protocol.c which was introduced in
+curl 8.20.0. In 8.7.1 the equivalent is changing connkeep() to
+connclose() in lib/smb.c, which prevents the connection from being
+returned to the pool. The effect is identical.
+
+Signed-off-by: Jaipaul Cheernam <jaipaul.cheernam@est.tech>
+---
+ lib/smb.c | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+diff --git a/lib/smb.c b/lib/smb.c
+index 7c73cbcec..a1f5c9b31 100644
+--- a/lib/smb.c
++++ b/lib/smb.c
+@@ -461,8 +461,7 @@ static CURLcode smb_connect(struct Curl_easy *data, bool *done)
+   if(!smbc->send_buf)
+     return CURLE_OUT_OF_MEMORY;
+ 
+-  /* Multiple requests are allowed with this connection */
+-  connkeep(conn, "SMB default");
++  connclose(conn, "SMB default");
+ 
+   /* Parse the username, domain, and password */
+   slash = strchr(conn->user, '/');

meta/recipes-support/curl/curl_8.7.1.bb

@@ -36,6 +36,7 @@ SRC_URI = " \
     file://CVE-2026-1965-2.patch \
     file://CVE-2026-3783.patch \
     file://CVE-2026-3784.patch \
+    file://CVE-2026-5773.patch \
 "
 
 SRC_URI:append:class-nativesdk = " \