diff --git a/src/gui/painting/qcolor.cpp b/src/gui/painting/qcolor.cpp
index e5bac84df98..858eba46219 100644
--- a/src/gui/painting/qcolor.cpp
+++ b/src/gui/painting/qcolor.cpp
@@ -88,6 +88,8 @@ static bool get_hex_rgb(const char *name, size_t len, QRgba64 *rgb)
         r = hex2int(name + 0, 3);
         g = hex2int(name + 3, 3);
         b = hex2int(name + 6, 3);
+        if (r == -1 || g == -1 || b == -1)
+            return false;
         r = (r << 4) | (r >> 8);
         g = (g << 4) | (g >> 8);
         b = (b << 4) | (b >> 8);
diff --git a/tests/auto/gui/painting/qcolor/tst_qcolor.cpp b/tests/auto/gui/painting/qcolor/tst_qcolor.cpp
index 17289e0b85e..f5bfa683d61 100644
--- a/tests/auto/gui/painting/qcolor/tst_qcolor.cpp
+++ b/tests/auto/gui/painting/qcolor/tst_qcolor.cpp
@@ -324,6 +324,9 @@ void tst_QColor::namehex_data()
     QTest::newRow("transparent red") << "#66ff0000" << QColor(255, 0, 0, 102);
     QTest::newRow("invalid red") << "#gg0000" << QColor();
     QTest::newRow("invalid transparent") << "#gg00ff00" << QColor();
+    // when configured with "-sanitize undefined", this resulted in:
+    // "runtime error: left shift of negative value -1"
+    QTest::newRow("oss-fuzz 23968") << "#ÿÿÿÿÿÿÿÿÿ" << QColor();
 }
 
 void tst_QColor::namehex()