libpng: patch CVE-2025-64506

Pick commit per NVD report.

(From OE-Core rev: eb4af9b4cea963b650be217d33bc12f560ed84a6)

Signed-off-by: Peter Marko <peter.marko@siemens.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

2 files changed, 58 insertions, 0 deletions

diff --git a/meta/recipes-multimedia/libpng/files/CVE-2025-64506.patch b/meta/recipes-multimedia/libpng/files/CVE-2025-64506.patch
new file mode 100644
index 0000000000..696f459971
--- /dev/null
+++ b/meta/recipes-multimedia/libpng/files/CVE-2025-64506.patch
@@ -0,0 +1,57 @@
+From 2bd84c019c300b78e811743fbcddb67c9d9bf821 Mon Sep 17 00:00:00 2001
+From: Cosmin Truta <ctruta@gmail.com>
+Date: Fri, 7 Nov 2025 22:40:05 +0200
+Subject: [PATCH] Fix a heap buffer overflow in `png_write_image_8bit`
+
+The condition guarding the pre-transform path incorrectly allowed 8-bit
+input data to enter `png_write_image_8bit` which expects 16-bit input.
+This caused out-of-bounds reads when processing 8-bit grayscale+alpha
+images (GitHub #688), or 8-bit RGB or RGB+alpha images (GitHub #746),
+with the `convert_to_8bit` flag set (an invalid combination that should
+bypass the pre-transform path).
+
+The second part of the condition, i.e.
+
+    colormap == 0 && convert_to_8bit != 0
+
+failed to verify that input was 16-bit, i.e.
+
+    linear != 0
+
+contradicting the comment "This only applies when the input is 16-bit".
+
+The fix consists in restructuring the condition to ensure both the
+`alpha` path and the `convert_to_8bit` path require linear (16-bit)
+input. The corrected condition, i.e.
+
+    linear != 0 && (alpha != 0 || display->convert_to_8bit != 0)
+
+matches the expectation of the `png_write_image_8bit` function and
+prevents treating 8-bit buffers as 16-bit data.
+
+Reported-by: Samsung-PENTEST <Samsung-PENTEST@users.noreply.github.com>
+Reported-by: weijinjinnihao <weijinjinnihao@users.noreply.github.com>
+Analyzed-by: degrigis <degrigis@users.noreply.github.com>
+Reviewed-by: John Bowler <jbowler@acm.org>
+
+CVE: CVE-2025-64506
+Upstream-Status: Backport [https://github.com/pnggroup/libpng/commit/2bd84c019c300b78e811743fbcddb67c9d9bf821]
+Signed-off-by: Peter Marko <peter.marko@siemens.com>
+---
+ pngwrite.c | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+diff --git a/pngwrite.c b/pngwrite.c
+index 35a5d17b6..83148960e 100644
+--- a/pngwrite.c
++++ b/pngwrite.c
+@@ -2129,8 +2129,7 @@ png_image_write_main(png_voidp argument)
+     * before it is written.  This only applies when the input is 16-bit and
+     * either there is an alpha channel or it is converted to 8-bit.
+     */
+-   if ((linear != 0 && alpha != 0 ) ||
+-       (colormap == 0 && display->convert_to_8bit != 0))
++   if (linear != 0 && (alpha != 0 || display->convert_to_8bit != 0))
+    {
+       png_bytep row = png_voidcast(png_bytep, png_malloc(png_ptr,
+           png_get_rowbytes(png_ptr, info_ptr)));
diff --git a/meta/recipes-multimedia/libpng/libpng_1.6.39.bb b/meta/recipes-multimedia/libpng/libpng_1.6.39.bb
index 62e3e81b4f..cc35e7a725 100644
--- a/meta/recipes-multimedia/libpng/libpng_1.6.39.bb
+++ b/meta/recipes-multimedia/libpng/libpng_1.6.39.bb
@@ -16,6 +16,7 @@ SRC_URI = "\
            file://CVE-2025-64505-01.patch \
            file://CVE-2025-64505-02.patch \
            file://CVE-2025-64505-03.patch \
+           file://CVE-2025-64506.patch \
 "
 
 SRC_URI[sha256sum] = "1f4696ce70b4ee5f85f1e1623dc1229b210029fa4b7aee573df3e2ba7b036937"