diff --git a/CHANGES.txt b/CHANGES.txt
index 6f6c1310d2..4eee4eef88 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -4,6 +4,7 @@
  * Don't resubmit counter mutation runnables internally (CASSANDRA-6427)
  * Don't drop local mutations without a trace (CASSANDRA-6510)
  * Don't allow null max_hint_window_in_ms (CASSANDRA-6419)
+ * Validate SliceRange start and finish lengths (CASSANDRA-6521)
 
 
 1.2.13
diff --git a/src/java/org/apache/cassandra/thrift/ThriftValidation.java b/src/java/org/apache/cassandra/thrift/ThriftValidation.java
index 5882e27f54..442ea4ea11 100644
--- a/src/java/org/apache/cassandra/thrift/ThriftValidation.java
+++ b/src/java/org/apache/cassandra/thrift/ThriftValidation.java
@@ -228,6 +228,15 @@ public class ThriftValidation
 
     public static void validateRange(CFMetaData metadata, ColumnParent column_parent, SliceRange range) throws org.apache.cassandra.exceptions.InvalidRequestException
     {
+        if (range.count < 0)
+            throw new org.apache.cassandra.exceptions.InvalidRequestException("get_slice requires non-negative count");
+
+        if (range.start.remaining() > IColumn.MAX_NAME_LENGTH)
+            throw new org.apache.cassandra.exceptions.InvalidRequestException("range start length cannot be larger than " + IColumn.MAX_NAME_LENGTH);
+
+        if (range.finish.remaining() > IColumn.MAX_NAME_LENGTH)
+            throw new org.apache.cassandra.exceptions.InvalidRequestException("range finish length cannot be larger than " + IColumn.MAX_NAME_LENGTH);
+
         AbstractType<?> comparator = metadata.getComparatorFor(column_parent.super_column);
         try
         {
@@ -239,9 +248,6 @@ public class ThriftValidation
             throw new org.apache.cassandra.exceptions.InvalidRequestException(e.getMessage());
         }
 
-        if (range.count < 0)
-            throw new org.apache.cassandra.exceptions.InvalidRequestException("get_slice requires non-negative count");
-
         Comparator<ByteBuffer> orderedComparator = range.isReversed() ? comparator.reverseComparator : comparator;
         if (range.start.remaining() > 0
             && range.finish.remaining() > 0