libxml2: Fix CVE-2026-86140

This patch applies the upstream fix as referenced in [2],
using the commit shown in [1].

[1] https://github.com/GNOME/libxml2/commit/d1686f91dbda141a752200419d35639fd6b38340
[2] https://nvd.nist.gov/vuln/detail/CVE-2026-86140

(From OE-Core rev: 2c45b60e5d543bca0c1a239254d879d1ad7e3a72)

Signed-off-by: Hetvi Thakar <hthakar@cisco.com>
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>

meta/recipes-core/libxml/libxml2/CVE-2026-86140.patch

@@ -0,0 +1,56 @@
+From 7d324fcfa71e8567678ad254c0e10e509ebae99b Mon Sep 17 00:00:00 2001
+From: mohammadmseet-hue <mohammadmseet@gmail.com>
+Date: Thu, 16 Apr 2026 02:54:37 +0200
+Subject: [PATCH] fix: add bounds checks to xmlSnprintfElements in valid.c
+
+CVE-2025-24928 fixed xmlSnprintfElementContent for unchecked strcat()
+writes, but the sibling function xmlSnprintfElements has the identical
+unfixed pattern. The strcat(buf, "(") before the while loop and
+strcat(buf, ")") after the loop exit have no bounds checks.
+
+Add remaining-space checks before both strcat calls, with early return
+and ellipsis when space is insufficient.
+
+CVE: CVE-2026-86140
+Upstream-Status: Backport [https://github.com/GNOME/libxml2/commit/d1686f91dbda141a752200419d35639fd6b38340]
+
+(cherry picked from commit d1686f91dbda141a752200419d35639fd6b38340)
+Signed-off-by: Hetvi Thakar <hthakar@cisco.com>
+---
+ valid.c | 16 ++++++++++++++--
+ 1 file changed, 14 insertions(+), 2 deletions(-)
+
+diff --git a/valid.c b/valid.c
+index ae4bb822..718e6d85 100644
+--- a/valid.c
++++ b/valid.c
+@@ -5047,7 +5047,15 @@ xmlSnprintfElements(char *buf, int size, xmlNodePtr node, int glob) {
+     int len;
+ 
+     if (node == NULL) return;
+-    if (glob) strcat(buf, "(");
++    len = strlen(buf);
++    if (glob) {
++        if (size - len < 50) {
++            if ((size - len > 4) && (buf[len - 1] != '.'))
++                strcat(buf, " ...");
++            return;
++        }
++        strcat(buf, "(");
++    }
+     cur = node;
+     while (cur != NULL) {
+ 	len = strlen(buf);
+@@ -5111,7 +5119,11 @@ xmlSnprintfElements(char *buf, int size, xmlNodePtr node, int glob) {
+ 	}
+ 	cur = cur->next;
+     }
+-    if (glob) strcat(buf, ")");
++    if (glob) {
++        len = strlen(buf);
++        if (size - len > 1)
++            strcat(buf, ")");
++    }
+ }
+ 
+ /**

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

@@ -34,6 +34,7 @@ SRC_URI += "http://www.w3.org/XML/Test/xmlts20130923.tar;subdir=${BP};name=testt
            file://CVE-2026-11979.patch \
            file://CVE-2026-86137.patch \
            file://CVE-2026-86138.patch \
+           file://CVE-2026-86140.patch \
            "
 
 SRC_URI[archive.sha256sum] = "c3d8c0c34aa39098f66576fe51969db12a5100b956233dc56506f7a8679be995"