libxml2: Fix CVE-2026-1757

Backport patch [1] to fix CVE-2026-1757.

The shell is refactored [2], so backport the related code from shell.c
to debugXML.c.

[1] https://gitlab.gnome.org/GNOME/libxml2/-/commit/160c8a43
[2] https://gitlab.gnome.org/GNOME/libxml2/-/commit/1341deac

(From OE-Core rev: decc9acf5aaa569e75f1e4986fb72530ad84c887)

Signed-off-by: Mingli Yu <mingli.yu@windriver.com>
Signed-off-by: Jinfeng Wang <jinfeng.wang.cn@windriver.com>
[YC: see https://security-tracker.debian.org/tracker/CVE-2026-1757 ]
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>

meta/recipes-core/libxml/libxml2/CVE-2026-1757.patch

@@ -0,0 +1,49 @@
+From bbe186902eddca01cc2049780a1d1a37937d3862 Mon Sep 17 00:00:00 2001
+From: Mingli Yu <mingli.yu@windriver.com>
+Date: Wed, 25 Feb 2026 16:16:14 +0800
+Subject: [PATCH] shell: free cmdline before continue
+
+This patch frees the cmdline when it's not empty but it doesn't contain
+any actual character.
+
+If the cmdline is just whitespaces or \r and \n, the loop continues
+without freeing the cmdline string, so it's a leak.
+
+Fix #1009
+
+Reference https://gitlab.gnome.org/GNOME/libxml2/-/commit/160c8a43
+
+CVE: CVE-2026-1757
+
+Upstream-Status: Backport [https://gitlab.gnome.org/GNOME/libxml2/-/commit/160c8a43]
+
+The shell is refactored [1], so backport the related code from shell.c
+to debugXML.c.
+
+[1] https://gitlab.gnome.org/GNOME/libxml2/-/commit/1341deac
+
+Signed-off-by: Mingli Yu <mingli.yu@windriver.com>
+---
+ debugXML.c | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/debugXML.c b/debugXML.c
+index 9d9618f..2d5c99d 100644
+--- a/debugXML.c
++++ b/debugXML.c
+@@ -2866,8 +2866,11 @@ xmlShell(xmlDocPtr doc, char *filename, xmlShellReadlineFunc input,
+             command[i++] = *cur++;
+         }
+         command[i] = 0;
+-        if (i == 0)
++        if (i == 0) {
++            free(cmdline);
++            cmdline = NULL;
+             continue;
++        }
+ 
+         /*
+          * Parse the argument
+-- 
+2.34.1
+

meta/recipes-core/libxml/libxml2_2.12.10.bb

@@ -30,6 +30,7 @@ SRC_URI += "http://www.w3.org/XML/Test/xmlts20130923.tar;subdir=${BP};name=testt
            file://CVE-2026-0992-01.patch \
            file://CVE-2026-0992-02.patch \
            file://CVE-2026-0992-03.patch \
+           file://CVE-2026-1757.patch \
            "
 
 SRC_URI[archive.sha256sum] = "c3d8c0c34aa39098f66576fe51969db12a5100b956233dc56506f7a8679be995"