gnutls: fix CVE-2026-42015

Backport patch to fix CVE-2026-42015.

References:
  https://nvd.nist.gov/vuln/detail/CVE-2026-42015

Upstream fix:
  https://gitlab.com/gnutls/gnutls/-/commit/a3e7c50d3e1761e5ef1d4b225507cab8f2b2c3ca

Tested with ptest

(From OE-Core rev: a069e8d76883bd23148b228eb6bac273ef3d01b7)

Signed-off-by: Jakub Szczudlo <jakub.szczudlo@nokia.com>
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>

meta/recipes-support/gnutls/gnutls/CVE-2026-42015.patch

@@ -0,0 +1,43 @@
+From a3e7c50d3e1761e5ef1d4b225507cab8f2b2c3ca Mon Sep 17 00:00:00 2001
+From: Alexander Sosedkin <asosedkin@redhat.com>
+Date: Mon, 20 Apr 2026 22:42:20 +0200
+Subject: [PATCH] x509/pkcs12_bag: fix off-by-one in bag element bounds check
+
+Appending elements to a PKCS#12 bag had a bounds check that
+prevented adding the 32nd element.
+On the other hand, it is possible to import one that already has 32.
+Subsequent appending then led to writing past the 32-element array,
+smashing its length.
+
+Tighten the check to reject any bag with 32 or more elements.
+
+We'll treat this vulnerability as a Low due to how contrived
+the requirements are: for the code to be vulnerable,
+it needs to append to an imported untrusted unencrypted PKCS#12 structure.
+
+Reported-by: Zou Dikai
+Fixes: #1840
+Fixes: CVE-2026-42015
+Fixes: GNUTLS-SA-2026-04-29-11
+CVSS: 6.1 Medium CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
+Severity: Low
+Signed-off-by: Alexander Sosedkin <asosedkin@redhat.com>
+
+CVE: CVE-2026-42015
+Upstream-Status: Backport [https://gitlab.com/gnutls/gnutls/-/commit/a3e7c50d3e1761e5ef1d4b225507cab8f2b2c3ca]
+
+Signed-off-by: Jakub Szczudlo <jakub.szczudlo@nokia.com>
+---
+diff --git a/lib/x509/pkcs12_bag.c b/lib/x509/pkcs12_bag.c
+index 911aeff..3822861 100644
+--- a/lib/x509/pkcs12_bag.c
++++ b/lib/x509/pkcs12_bag.c
+@@ -375,7 +375,7 @@ int gnutls_pkcs12_bag_set_data(gnutls_pkcs12_bag_t bag,
+ 		return GNUTLS_E_INVALID_REQUEST;
+ 	}
+ 
+-	if (bag->bag_elements == MAX_BAG_ELEMENTS - 1) {
++	if (bag->bag_elements >= MAX_BAG_ELEMENTS - 1) {
+ 		gnutls_assert();
+ 		/* bag is full */
+ 		return GNUTLS_E_MEMORY_ERROR;

meta/recipes-support/gnutls/gnutls_3.8.4.bb

@@ -59,6 +59,7 @@ SRC_URI = "https://www.gnupg.org/ftp/gcrypt/gnutls/v${SHRT_VER}/gnutls-${PV}.tar
            file://CVE-2026-42013-pre1.patch \
            file://CVE-2026-42013.patch \
            file://CVE-2026-42014.patch \
+           file://CVE-2026-42015.patch \
            "
 
 SRC_URI[sha256sum] = "2bea4e154794f3f00180fa2a5c51fe8b005ac7a31cd58bd44cdfa7f36ebc3a9b"