libpng: patch CVE-2025-64720

Pick commit per NVD report.

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

diff --git a/meta/recipes-multimedia/libpng/files/CVE-2025-64720.patch b/meta/recipes-multimedia/libpng/files/CVE-2025-64720.patch
new file mode 100644 (file)
index 0000000..08df7c3
--- /dev/null
+++ b/meta/recipes-multimedia/libpng/files/CVE-2025-64720.patch
@@ -0,0 +1,103 @@
+From 08da33b4c88cfcd36e5a706558a8d7e0e4773643 Mon Sep 17 00:00:00 2001
+From: Cosmin Truta <ctruta@gmail.com>
+Date: Wed, 12 Nov 2025 13:46:23 +0200
+Subject: [PATCH] Fix a buffer overflow in `png_init_read_transformations`
+
+The palette compositing code in `png_init_read_transformations` was
+incorrectly applying background compositing when PNG_FLAG_OPTIMIZE_ALPHA
+was set. This violated the premultiplied alpha invariant
+`component <= alpha` expected by `png_image_read_composite`, causing
+values that exceeded the valid range for the PNG_sRGB_FROM_LINEAR lookup
+tables.
+
+When PNG_ALPHA_OPTIMIZED is active, palette entries should contain pure
+premultiplied RGB values without background compositing. The background
+compositing must happen later in `png_image_read_composite` where the
+actual background color from the PNG file is available.
+
+The fix consists in introducing conditional behavior based on
+PNG_FLAG_OPTIMIZE_ALPHA: when set, the code performs only
+premultiplication using the formula `component * alpha + 127) / 255`
+with proper gamma correction. When not set, the original background
+compositing calculation based on the `png_composite` macro is preserved.
+
+This prevents buffer overflows in `png_image_read_composite` where
+out-of-range premultiplied values would cause out-of-bounds array access
+in `png_sRGB_base[]` and `png_sRGB_delta[]`.
+
+Reported-by: Samsung-PENTEST <Samsung-PENTEST@users.noreply.github.com>
+Analyzed-by: John Bowler <jbowler@acm.org>
+
+CVE: CVE-2025-64720
+Upstream-Status: Backport [https://github.com/pnggroup/libpng/commit/08da33b4c88cfcd36e5a706558a8d7e0e4773643]
+Signed-off-by: Peter Marko <peter.marko@siemens.com>
+---
+ pngrtran.c | 52 ++++++++++++++++++++++++++++++++++++++++++----------
+ 1 file changed, 42 insertions(+), 10 deletions(-)
+
+diff --git a/pngrtran.c b/pngrtran.c
+index 548780030..2f5202255 100644
+--- a/pngrtran.c
++++ b/pngrtran.c
+@@ -1698,19 +1698,51 @@ png_init_read_transformations(png_structrp png_ptr)
+                   }
+                   else /* if (png_ptr->trans_alpha[i] != 0xff) */
+                   {
+-                     png_byte v, w;
++                     if ((png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0)
++                     {
++                        /* Premultiply only:
++                         * component = round((component * alpha) / 255)
++                         */
++                        png_uint_32 component;
+ 
+-                     v = png_ptr->gamma_to_1[palette[i].red];
+-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
+-                     palette[i].red = png_ptr->gamma_from_1[w];
++                        component = png_ptr->gamma_to_1[palette[i].red];
++                        component =
++                            (component * png_ptr->trans_alpha[i] + 128) / 255;
++                        palette[i].red = png_ptr->gamma_from_1[component];
+ 
+-                     v = png_ptr->gamma_to_1[palette[i].green];
+-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
+-                     palette[i].green = png_ptr->gamma_from_1[w];
++                        component = png_ptr->gamma_to_1[palette[i].green];
++                        component =
++                            (component * png_ptr->trans_alpha[i] + 128) / 255;
++                        palette[i].green = png_ptr->gamma_from_1[component];
+ 
+-                     v = png_ptr->gamma_to_1[palette[i].blue];
+-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
+-                     palette[i].blue = png_ptr->gamma_from_1[w];
++                        component = png_ptr->gamma_to_1[palette[i].blue];
++                        component =
++                            (component * png_ptr->trans_alpha[i] + 128) / 255;
++                        palette[i].blue = png_ptr->gamma_from_1[component];
++                     }
++                     else
++                     {
++                        /* Composite with background color:
++                         * component =
++                         *    alpha * component + (1 - alpha) * background
++                         */
++                        png_byte v, w;
++
++                        v = png_ptr->gamma_to_1[palette[i].red];
++                        png_composite(w, v,
++                            png_ptr->trans_alpha[i], back_1.red);
++                        palette[i].red = png_ptr->gamma_from_1[w];
++
++                        v = png_ptr->gamma_to_1[palette[i].green];
++                        png_composite(w, v,
++                            png_ptr->trans_alpha[i], back_1.green);
++                        palette[i].green = png_ptr->gamma_from_1[w];
++
++                        v = png_ptr->gamma_to_1[palette[i].blue];
++                        png_composite(w, v,
++                            png_ptr->trans_alpha[i], back_1.blue);
++                        palette[i].blue = png_ptr->gamma_from_1[w];
++                     }
+                   }
+                }
+                else

diff --git a/meta/recipes-multimedia/libpng/libpng_1.6.42.bb b/meta/recipes-multimedia/libpng/libpng_1.6.42.bb
index ab043e33384585709f58aceac21e5e708b1a9d92..6f5b69b75404db7627e117b38ae97afb828a1c03 100644 (file)
--- a/meta/recipes-multimedia/libpng/libpng_1.6.42.bb
+++ b/meta/recipes-multimedia/libpng/libpng_1.6.42.bb
@@ -16,6 +16,7 @@ SRC_URI = "${SOURCEFORGE_MIRROR}/project/${BPN}/${BPN}${LIBV}/${PV}/${BP}.tar.xz
            file://CVE-2025-64505-02.patch \
            file://CVE-2025-64505-03.patch \
            file://CVE-2025-64506.patch \
+           file://CVE-2025-64720.patch \
 "
 
 SRC_URI[sha256sum] = "c919dbc11f4c03b05aba3f8884d8eb7adfe3572ad228af972bb60057bdb48450"