[OE-core][scarthgap][PATCH 01/10] expat: fix CVE-2026-56403

["Deepak Rathore -X (deeratho - E INFOCHIPS PRIVATE LIMITED at Cisco)" <deeratho@cisco.com>]

From: Deepak Rathore <deeratho@cisco.com>

These patches apply the upstream fixes shown in [1] and [2], as
referenced by [3].

Upstream pull request mentioned in [4] contains both the storeAtts fix
and the related xcsdup overflow hardening so adding both source patches
explicit, even though the published advisory description names storeAtts
specifically.

[1] https://github.com/libexpat/libexpat/commit/12dc6d8d3d65f79471a94d8565f6bf1cf245f648
[2] https://github.com/libexpat/libexpat/commit/147c8f36d6277d5c6011c098370a8362aed47b15
[3] https://nvd.nist.gov/vuln/detail/CVE-2026-56403
[4] https://github.com/libexpat/libexpat/pull/1232

Signed-off-by: Deepak Rathore <deeratho@cisco.com>
---
 .../expat/expat/CVE-2026-56403_p1.patch       | 81 +++++++++++++++++++
 .../expat/expat/CVE-2026-56403_p2.patch       | 52 ++++++++++++
 meta/recipes-core/expat/expat_2.6.4.bb        |  2 +
 3 files changed, 135 insertions(+)
 create mode 100644 meta/recipes-core/expat/expat/CVE-2026-56403_p1.patch
 create mode 100644 meta/recipes-core/expat/expat/CVE-2026-56403_p2.patch

diff --git a/meta/recipes-core/expat/expat/CVE-2026-56403_p1.patch b/meta/recipes-core/expat/expat/CVE-2026-56403_p1.patch
new file mode 100644
index 0000000000..f5e55eb6e3
--- /dev/null
+++ b/meta/recipes-core/expat/expat/CVE-2026-56403_p1.patch
@@ -0,0 +1,81 @@
+From b689559597116ee75a633453e2f7177c8541b04e Mon Sep 17 00:00:00 2001
+From: Sebastian Pipping <sebastian@pipping.org>
+Date: Wed, 20 May 2026 12:12:10 +0200
+Subject: [PATCH 01/17] lib: Protect function `storeAtts` from signed integer
+ overflow
+
+CVE: CVE-2026-56403
+Upstream-Status: Backport [https://github.com/libexpat/libexpat/commit/12dc6d8d3d65f79471a94d8565f6bf1cf245f648]
+
+Backport Changes:
+- Adapt storeAtts to the Scarthgap 2.6.4 loop and URI allocation
+  logic while preserving the upstream overflow checks.
+
+(cherry picked from commit 12dc6d8d3d65f79471a94d8565f6bf1cf245f648)
+Signed-off-by: Deepak Rathore <deeratho@cisco.com>
+---
+ expat/lib/xmlparse.c | 30 ++++++++++++++++++++----------
+ 1 file changed, 20 insertions(+), 10 deletions(-)
+
+diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
+index 9bc67f38..df92a3ca 100644
+--- a/expat/lib/xmlparse.c
++++ b/expat/lib/xmlparse.c
+@@ -4226,26 +4226,32 @@ storeAtts(XML_Parser parser, const ENCODING *enc, const char *attStr,
+     return XML_ERROR_NONE;
+   prefixLen = 0;
+   if (parser->m_ns_triplets && binding->prefix->name) {
+-    for (; binding->prefix->name[prefixLen++];)
+-      ; /* prefixLen includes null terminator */
++    size_t candidateLen = 0;
++    for (; binding->prefix->name[candidateLen++];)
++      ; /* candidateLen includes null terminator */
++    /* Detect and prevent integer overflow */
++    if (candidateLen > INT_MAX)
++      return XML_ERROR_NO_MEMORY;
++    prefixLen = (int)candidateLen;
+   }
+   tagNamePtr->localPart = localPart;
+   tagNamePtr->uriLen = binding->uriLen;
+   tagNamePtr->prefix = binding->prefix->name;
+   tagNamePtr->prefixLen = prefixLen;
+-  for (i = 0; localPart[i++];)
+-    ; /* i includes null terminator */
++
++  size_t localPartLen = 0;
++  for (; localPart[localPartLen++];)
++    ; /* localPartLen includes null terminator */
+ 
+   /* Detect and prevent integer overflow */
+-  if (binding->uriLen > INT_MAX - prefixLen
+-      || i > INT_MAX - (binding->uriLen + prefixLen)) {
++  if (localPartLen > INT_MAX || binding->uriLen > INT_MAX - prefixLen
++      || localPartLen > (size_t)INT_MAX - (binding->uriLen + prefixLen)) {
+     return XML_ERROR_NO_MEMORY;
+   }
+ 
+-  n = i + binding->uriLen + prefixLen;
++  n = (int)localPartLen + binding->uriLen + prefixLen;
+   if (n > binding->uriAlloc) {
+     TAG *p;
+-
+     /* Detect and prevent integer overflow */
+     if (n > INT_MAX - EXPAND_SPARE) {
+       return XML_ERROR_NO_MEMORY;
+@@ -4273,10 +4279,14 @@ storeAtts(XML_Parser parser, const ENCODING *enc, const char *attStr,
+   }
+   /* if m_namespaceSeparator != '\0' then uri includes it already */
+   uri = binding->uri + binding->uriLen;
+-  memcpy(uri, localPart, i * sizeof(XML_Char));
++  /* Detect and prevent integer overflow */
++  if (localPartLen > SIZE_MAX / sizeof(XML_Char)) {
++    return XML_ERROR_NO_MEMORY;
++  }
++  memcpy(uri, localPart, localPartLen * sizeof(XML_Char));
+   /* we always have a namespace separator between localPart and prefix */
+   if (prefixLen) {
+-    uri += i - 1;
++    uri += localPartLen - 1;
+     *uri = parser->m_namespaceSeparator; /* replace null terminator */
+     memcpy(uri + 1, binding->prefix->name, prefixLen * sizeof(XML_Char));
+   }
diff --git a/meta/recipes-core/expat/expat/CVE-2026-56403_p2.patch b/meta/recipes-core/expat/expat/CVE-2026-56403_p2.patch
new file mode 100644
index 0000000000..b578cb60cc
--- /dev/null
+++ b/meta/recipes-core/expat/expat/CVE-2026-56403_p2.patch
@@ -0,0 +1,52 @@
+From 2855ce68a1ce9732267c06734427930364ab66c1 Mon Sep 17 00:00:00 2001
+From: Sebastian Pipping <sebastian@pipping.org>
+Date: Fri, 22 May 2026 00:43:52 +0200
+Subject: [PATCH 02/17] xmlwf: Protect function `xcsdup` from signed integer
+ overflow
+
+CVE: CVE-2026-56403
+Upstream-Status: Backport [https://github.com/libexpat/libexpat/commit/147c8f36d6277d5c6011c098370a8362aed47b15]
+
+Backport Changes:
+- Add stdint.h and convert count and numBytes to size_t because
+  Scarthgap 2.6.4 lacks these upstream prerequisites.
+
+(cherry picked from commit 147c8f36d6277d5c6011c098370a8362aed47b15)
+Signed-off-by: Deepak Rathore <deeratho@cisco.com>
+---
+ expat/xmlwf/xmlwf.c | 10 ++++++++--
+ 1 file changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/expat/xmlwf/xmlwf.c b/expat/xmlwf/xmlwf.c
+index fd4fc3f8..7bbdb303 100644
+--- a/expat/xmlwf/xmlwf.c
++++ b/expat/xmlwf/xmlwf.c
+@@ -45,6 +45,7 @@
+ 
+ #include <assert.h>
+ #include <stdio.h>
++#include <stdint.h>
+ #include <stdlib.h>
+ #include <stddef.h>
+ #include <string.h>
+@@ -304,13 +305,18 @@ processingInstruction(void *userData, const XML_Char *target,
+ static XML_Char *
+ xcsdup(const XML_Char *s) {
+   XML_Char *result;
+-  int count = 0;
+-  int numBytes;
++  size_t count = 0;
++  size_t numBytes;
+ 
+   /* Get the length of the string, including terminator */
+   while (s[count++] != 0) {
+     /* Do nothing */
+   }
++
++  // Detect and prevent integer overflow
++  if (count > SIZE_MAX / sizeof(XML_Char))
++    return NULL;
++
+   numBytes = count * sizeof(XML_Char);
+   result = malloc(numBytes);
+   if (result == NULL)
diff --git a/meta/recipes-core/expat/expat_2.6.4.bb b/meta/recipes-core/expat/expat_2.6.4.bb
index 151720a9e3..dba4b2c81d 100644
--- a/meta/recipes-core/expat/expat_2.6.4.bb
+++ b/meta/recipes-core/expat/expat_2.6.4.bb
@@ -51,6 +51,8 @@ SRC_URI = "${GITHUB_BASE_URI}/download/R_${VERSION_TAG}/expat-${PV}.tar.bz2  \
            file://CVE-2026-32777-02.patch \
            file://CVE-2026-32778-01.patch \
            file://CVE-2026-32778-02.patch \
+           file://CVE-2026-56403_p1.patch;striplevel=2 \
+           file://CVE-2026-56403_p2.patch;striplevel=2 \
            "
 
 GITHUB_BASE_URI = "https://github.com/libexpat/libexpat/releases/"