diff -urNp xerces-c-3.1.1/src/xercesc/internal/XMLReader.cpp xerces-c-3.1.1-patch/src/xercesc/internal/XMLReader.cpp
--- xerces-c-3.1.1/src/xercesc/internal/XMLReader.cpp	2010-01-20 12:06:14.000000000 -0500
+++ xerces-c-3.1.1-patch/src/xercesc/internal/XMLReader.cpp	2015-06-22 12:20:22.131498873 -0400
@@ -1460,6 +1460,17 @@ void XMLReader::doInitDecode()
 
             while (fRawBufIndex < fRawBytesAvail)
             {
+                // Security fix: make sure there are at least sizeof(UCS4Ch) bytes to consume.
+                if (fRawBufIndex + sizeof(UCS4Ch) > fRawBytesAvail) {
+                    ThrowXMLwithMemMgr1
+                    (
+                        TranscodingException
+                        , XMLExcepts::Reader_CouldNotDecodeFirstLine
+                        , fSystemId
+                        , fMemoryManager
+                    );
+                }
+
                 // Get out the current 4 byte value and inc our raw buf index
                 UCS4Ch curVal = *asUCS++;
                 fRawBufIndex += sizeof(UCS4Ch);
@@ -1619,6 +1630,17 @@ void XMLReader::doInitDecode()
 
             while (fRawBufIndex < fRawBytesAvail)
             {
+                // Security fix: make sure there are at least sizeof(UTF16Ch) bytes to consume.
+                if (fRawBufIndex + sizeof(UTF16Ch) > fRawBytesAvail) {
+                    ThrowXMLwithMemMgr1
+                    (
+                        TranscodingException
+                        , XMLExcepts::Reader_CouldNotDecodeFirstLine
+                        , fSystemId
+                        , fMemoryManager
+                    );
+                }
+
                 // Get out the current 2 byte value
                 UTF16Ch curVal = *asUTF16++;
                 fRawBufIndex += sizeof(UTF16Ch);
@@ -1708,6 +1730,17 @@ void XMLReader::doInitDecode()
 //
 void XMLReader::refreshRawBuffer()
 {
+    // Security fix: make sure we don't underflow on the subtraction.
+    if (fRawBufIndex > fRawBytesAvail) {
+        ThrowXMLwithMemMgr1
+        (
+            RuntimeException
+            , XMLExcepts::Str_StartIndexPastEnd
+            , fSystemId
+            , fMemoryManager
+        );
+    }
+
     //
     //  If there are any bytes left, move them down to the start. There
     //  should only ever be (max bytes per char - 1) at the most.