2 files changed, 10 insertions, 2 deletions
diff --git a/sal/inc/rtl/strbuf.hxx b/sal/inc/rtl/strbuf.hxx
index 4dabc7653e7b..d858c89023da 100644
--- a/sal/inc/rtl/strbuf.hxx
+++ b/sal/inc/rtl/strbuf.hxx
@@ -417,7 +417,11 @@ public:
 
       @since LibreOffice 3.5
     */
-    sal_Char & operator [](sal_Int32 index) { return pData->buffer[index]; }
+    sal_Char & operator [](sal_Int32 index)
+    {
+        assert(index >= 0 && index < pData->length);
+        return pData->buffer[index];
+    }
 
     /**
         Return a OString instance reflecting the current content
diff --git a/sal/inc/rtl/ustrbuf.hxx b/sal/inc/rtl/ustrbuf.hxx
index 95993fc4a12c..abbf3d01ade5 100644
--- a/sal/inc/rtl/ustrbuf.hxx
+++ b/sal/inc/rtl/ustrbuf.hxx
@@ -409,7 +409,11 @@ public:
 
       @since LibreOffice 3.5
     */
-    sal_Unicode & operator [](sal_Int32 index) { return pData->buffer[index]; }
+    sal_Unicode & operator [](sal_Int32 index)
+    {
+        assert(index >= 0 && index < pData->length);
+        return pData->buffer[index];
+    }
 
     /**
         Return a OUString instance reflecting the current content