diff --git a/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/EllipticalArcTo.java b/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/EllipticalArcTo.java
index 1dcb6cbdfc..99561a6a7d 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/EllipticalArcTo.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/EllipticalArcTo.java
@@ -73,6 +73,10 @@ public class EllipticalArcTo implements GeometryRow {
         for (CellType cell : row.getCellArray()) {
             String cellName = cell.getN();
 
+            if (cellName == null) {
+                throw new POIXMLException("Missing cellName in EllipticalArcTo row");
+            }
+
             switch (cellName) {
                 case "X":
                     x = XDGFCell.parseDoubleValue(cell);
diff --git a/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-5842659694215168.vsdx b/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-5842659694215168.vsdx
new file mode 100644
index 0000000000..e6e6a3a902
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diff --git a/test-data/spreadsheet/stress.xls b/test-data/spreadsheet/stress.xls
index 24d91b2661..790188dda0 100644
Binary files a/test-data/spreadsheet/stress.xls and b/test-data/spreadsheet/stress.xls differ