diff --git a/src/hb-ot-layout-common.hh b/src/hb-ot-layout-common.hh
index f1288efab..0509da716 100644
--- a/src/hb-ot-layout-common.hh
+++ b/src/hb-ot-layout-common.hh
@@ -3020,6 +3020,8 @@ struct VarData
 
     unsigned ri_count = ri_map.get_population ();
     regionIndices.len = ri_count;
+    if (unlikely (hb_unsigned_mul_overflows (get_row_size (), itemCount)))
+      return_trace (false);
     if (unlikely (!c->extend (this))) return_trace (false);
 
     for (unsigned r = 0; r < ri_count; r++)
@@ -3124,6 +3126,8 @@ struct VarData
 
     regionIndices.len = new_ri_count;
 
+    if (unlikely (hb_unsigned_mul_overflows (get_row_size (), itemCount)))
+      return_trace (false);
     if (unlikely (!c->extend (this))) return_trace (false);
 
     for (r = 0; r < new_ri_count; r++)