diff --git a/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/NURBSTo.java b/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/NURBSTo.java
index e3d6f59eb8..deb00115c2 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/NURBSTo.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/NURBSTo.java
@@ -67,6 +67,9 @@ public class NURBSTo implements GeometryRow {
 
         for (CellType cell : row.getCellArray()) {
             String cellName = cell.getN();
+            if (cellName == null) {
+                throw new POIXMLException("Invalid null-cell in NURBS row");
+            }
 
             switch (cellName) {
                 case "X":
diff --git a/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-4513310052515840.vsdx b/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-4513310052515840.vsdx
new file mode 100644
index 0000000000..2e316f8730
Binary files /dev/null and b/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-4513310052515840.vsdx differ
diff --git a/test-data/spreadsheet/stress.xls b/test-data/spreadsheet/stress.xls
index 4c9c65f32a..f4d52ecf69 100644
Binary files a/test-data/spreadsheet/stress.xls and b/test-data/spreadsheet/stress.xls differ