diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8e63627..5900478 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -47,7 +47,6 @@
 * The --grid flag in avifenc can be used for images that are not evenly divided
   into cells.
 * Apps must be built with libpng version 1.6.32 or above.
-* Update svt.cmd/svt.sh: v1.5.0
 * avifImageCopy() no longer accepts source U and V channels to be NULL for
   non-4:0:0 input if Y is not NULL and if AVIF_PLANES_YUV is specified.
 * The default values of the maxQuantizer and maxQuantizerAlpha members of
@@ -62,6 +61,8 @@
 * Update aom.cmd: v3.6.1
 * Update dav1d.cmd: 1.2.0
 * Update rav1e.cmd: v0.6.3
+* Update svt.cmd/svt.sh: v1.5.0
+* Update zlibpng.cmd: zlib 1.2.13 and libpng 1.6.39
 * avifImageCreate(), avifImageCreateEmpty(), avifEncoderCreate() and other
   internal functions now return NULL if a memory allocation failed.
 * avifEncoderSetCodecSpecificOption() now returns avifResult instead of void to
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 21a494f..d359914 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -90,10 +90,10 @@
 option(AVIF_LOCAL_ZLIBPNG "Build zlib and libpng by providing your own copy inside the ext subdir." OFF)
 if(AVIF_LOCAL_ZLIBPNG)
     add_subdirectory(ext/zlib)
-    # Put the value of ZLIB_INCLUDE_DIR in the cache. This works around cmake behavior that has been updated by
+    # Put the value of ZLIB_INCLUDE_DIRS in the cache. This works around cmake behavior that has been updated by
     # cmake policy CMP0102 in cmake 3.17. Remove the CACHE workaround when we require cmake 3.17 or later. See
     # https://gitlab.kitware.com/cmake/cmake/-/issues/21343.
-    set(ZLIB_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ext/zlib" CACHE PATH "zlib include dir")
+    set(ZLIB_INCLUDE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/ext/zlib" CACHE PATH "zlib include dir")
     include_directories("${CMAKE_CURRENT_BINARY_DIR}/ext/zlib")
     set(CMAKE_DEBUG_POSTFIX "")
 
diff --git a/ext/zlibpng.cmd b/ext/zlibpng.cmd
index f07504e..0b9af7b 100755
--- a/ext/zlibpng.cmd
+++ b/ext/zlibpng.cmd
@@ -4,5 +4,5 @@
 
 : # The odd choice of comment style in this file is to try to share this script between *nix and win32.
 
-git clone -b v1.2.12 --depth 1 https://github.com/madler/zlib.git
-git clone -b v1.6.37 --depth 1 https://github.com/glennrp/libpng.git
+git clone -b v1.2.13 --depth 1 https://github.com/madler/zlib.git
+git clone -b v1.6.39 --depth 1 https://github.com/glennrp/libpng.git