diff --git a/CMakeLists.txt b/CMakeLists.txt
index 588800b3..93b3c743 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1120,8 +1120,7 @@ endif()
 ################################
 if( ENABLE_VTK )
     set( VTK_DIR "${CMAKE_INSTALL_PREFIX}/vtk" )
-    set( VTK_URL "${TPL_MIRROR_DIR}/VTK-9.4.2.tar.gz" )
-
+    set( VTK_URL "${TPL_MIRROR_DIR}/VTK-v9.6.0.tar.gz" )
     message( STATUS "Building VTK found at ${VTK_URL}" )
 
     # Depending on the platform, the install directory could be 'lib' or 'lib64'.
diff --git a/scripts/spack_packages/packages/geosx/package.py b/scripts/spack_packages/packages/geosx/package.py
index 3bcac0cb..90a4689d 100644
--- a/scripts/spack_packages/packages/geosx/package.py
+++ b/scripts/spack_packages/packages/geosx/package.py
@@ -157,7 +157,7 @@ class Geosx(CMakePackage, CudaPackage, ROCmPackage):
     depends_on('pugixml@1.13 ~shared')
 
     depends_on('fmt@10.0.0 cxxstd=14')
-    depends_on('vtk@9.4.2', when='+vtk')
+    depends_on('vtk@9.6.0', when='+vtk')
 
     #
     # Math
diff --git a/scripts/spack_packages/packages/vtk/9.6.0-patch/vtkCellGridReader.cxx.patch b/scripts/spack_packages/packages/vtk/9.6.0-patch/vtkCellGridReader.cxx.patch
new file mode 100644
index 00000000..600acf61
--- /dev/null
+++ b/scripts/spack_packages/packages/vtk/9.6.0-patch/vtkCellGridReader.cxx.patch
@@ -0,0 +1,14 @@
+--- a/IO/CellGrid/vtkCellGridReader.cxx	2025-03-27 23:59:55
++++ b/IO/CellGrid/vtkCellGridReader.cxx	2025-04-15 13:17:03
+@@ -419,7 +419,10 @@
+       // The final "false" below allows the data to not be fully consumed,
+       // which may happen if sizeof(istream::char_type) > 1. In the future,
+       // it may also happen that a file contains multiple JSON streams.
+-      jj = nlohmann::json::from_msgpack(data.begin(), data.end(), false);
++
++      char const * const begin = reinterpret_cast<const char*>(data.data());
++      char const * const end = begin + data.size();
++      jj = nlohmann::json::from_msgpack(begin, end, false);
+     }
+     catch (...)
+     {
diff --git a/scripts/spack_packages/packages/vtk/9.6.0-patch/vtkLegacyCellGridReader.cxx.patch b/scripts/spack_packages/packages/vtk/9.6.0-patch/vtkLegacyCellGridReader.cxx.patch
new file mode 100644
index 00000000..3ce4667c
--- /dev/null
+++ b/scripts/spack_packages/packages/vtk/9.6.0-patch/vtkLegacyCellGridReader.cxx.patch
@@ -0,0 +1,14 @@
+--- a/IO/Legacy/vtkLegacyCellGridReader.cxx	2025-03-27 23:59:55
++++ b/IO/Legacy/vtkLegacyCellGridReader.cxx	2025-04-15 13:28:24
+@@ -116,7 +116,10 @@
+       // The final argument (false) indicates that the decoder should allow
+       // partial consumption of raw.data() (meaning the trailing newline will
+       // not cause an exception):
+-      jdata = nlohmann::json::from_msgpack(raw.data(), raw.data() + contentLength, false);
++
++      char const * const begin = reinterpret_cast<const char*>(raw.data());
++      char const * const end = begin + contentLength;
++      jdata = nlohmann::json::from_msgpack(begin, end, false);
+     }
+     catch (nlohmann::json::exception& e)
+     {
diff --git a/scripts/spack_packages/packages/vtk/package.py b/scripts/spack_packages/packages/vtk/package.py
index c75d6cfe..d5cf2ea3 100644
--- a/scripts/spack_packages/packages/vtk/package.py
+++ b/scripts/spack_packages/packages/vtk/package.py
@@ -15,12 +15,14 @@ class Vtk(CMakePackage):
     processing and visualization. """
 
     homepage = "http://www.vtk.org"
-    url = "https://www.vtk.org/files/release/9.4/VTK-9.4.2.tar.gz"
+    #url = "https://www.vtk.org/files/release/9.4/VTK-9.4.2.tar.gz"
+    git = "https://gitlab.kitware.com/vtk/vtk.git"
     list_url = "http://www.vtk.org/download/"
 
     maintainers = ['chuckatkins', 'danlipsa']
     
-    version("9.4.2", sha256="36c98e0da96bb12a30fe53708097aa9492e7b66d5c3b366e1c8dc251e2856a02", preferred=True)
+    version("9.6.0", tag="v9.6.0", branch="master", get_full_repo=True)
+    version("9.4.2", sha256="36c98e0da96bb12a30fe53708097aa9492e7b66d5c3b366e1c8dc251e2856a02")
     version("9.3.1", sha256="8354ec084ea0d2dc3d23dbe4243823c4bfc270382d0ce8d658939fd50061cab8")
     version("9.2.6", sha256="06fc8d49c4e56f498c40fcb38a563ed8d4ec31358d0101e8988f0bb4d539dd12")
     version('9.1.0', sha256='8fed42f4f8f1eb8083107b68eaa9ad71da07110161a3116ad807f43e5ca5ce96')
@@ -57,12 +59,12 @@ class Vtk(CMakePackage):
     depends_on('mpi', when='+mpi')
 
     
-    patch_dir = os.path.join(os.path.dirname(__file__), '9.4.2-patch')
+    patch_dir = os.path.join(os.path.dirname(__file__), '9.6.0-patch')
     if os.path.isdir(patch_dir):
         for fname in sorted(os.listdir(patch_dir)):
                full_path = os.path.join(patch_dir, fname)
                if fname.endswith('.patch') and os.path.isfile(full_path):
-                   patch(os.path.join('9.4.2-patch', fname), when='@9.4.2')
+                   patch(os.path.join('9.6.0-patch', fname), when='@9.6.0')
 
     def cmake_args(self):
         spec = self.spec
diff --git a/tplMirror/VTK-9.4.2.tar.gz b/tplMirror/VTK-9.4.2.tar.gz
deleted file mode 100644
index 4a9c9cc5..00000000
--- a/tplMirror/VTK-9.4.2.tar.gz
+++ /dev/null
@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:36c98e0da96bb12a30fe53708097aa9492e7b66d5c3b366e1c8dc251e2856a02
-size 118621433
diff --git a/tplMirror/vtk-v9.6.0.tar.gz b/tplMirror/vtk-v9.6.0.tar.gz
new file mode 100644
index 00000000..4323c209
--- /dev/null
+++ b/tplMirror/vtk-v9.6.0.tar.gz
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:b48dd64a6c474d3d9425dcb549bff277753a9a56a3d08231e42598ce8e79521a
+size 54146584