--- old/src/share/classes/com/sun/imageio/plugins/png/PNGImageReader.java	2014-05-08 22:26:35.056284800 +0400
+++ new/src/share/classes/com/sun/imageio/plugins/png/PNGImageReader.java	2014-05-08 22:26:34.895264300 +0400
@@ -664,6 +664,12 @@
             try {
                 while (true) {
                     int chunkLength = stream.readInt();
+
+                    // verify the chunk length first
+                    if (chunkLength < 0 || chunkLength + 4 < 0) {
+                        throw new IIOException("Invalid chunk lenght " + chunkLength);
+                    }
+
                     int chunkType = stream.readInt();
 
                     if (chunkType == IDAT_TYPE) {
--- /dev/null	2014-05-08 22:26:36.000000000 +0400
+++ new/test/javax/imageio/plugins/png/ReadMalformedPngTest.java	2014-05-08 22:26:36.451461900 +0400
@@ -0,0 +1,160 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug     6945174
+ * @summary Test verifies that PNG image readr throw correct exception if image contains
+ *          a chunk with incorrect length.
+ * @run     main ReadMalformedPngTest
+ */
+
+import java.awt.Color;
+import java.awt.GradientPaint;
+import java.awt.Graphics2D;
+import java.awt.image.BufferedImage;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import javax.imageio.IIOException;
+import javax.imageio.IIOImage;
+import javax.imageio.ImageIO;
+import javax.imageio.ImageTypeSpecifier;
+import javax.imageio.ImageWriteParam;
+import javax.imageio.ImageWriter;
+import javax.imageio.metadata.IIOMetadata;
+import javax.imageio.metadata.IIOMetadataNode;
+import javax.imageio.stream.ImageOutputStream;
+import org.w3c.dom.Node;
+
+public class ReadMalformedPngTest {
+
+    public static void main(String[] args) throws IOException {
+        ByteArrayInputStream bais = new ByteArrayInputStream(createTestPng());
+
+        IIOException expected = null;
+        try {
+            ImageIO.read(bais);
+        } catch (IIOException e) {
+            expected = e;
+        } catch (Throwable e) {
+            throw new RuntimeException("Test failed!", e);
+        }
+
+        if (expected == null) {
+            throw new RuntimeException("Test failed.");
+        }
+
+        System.out.println("Test passed.");
+    }
+
+    private static byte[] createTestPng() throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+
+        BufferedImage img = createTestImage();
+
+        try {
+            ImageOutputStream ios = ImageIO.createImageOutputStream(baos);
+
+            ImageWriter w = ImageIO.getImageWritersByFormatName("PNG").next();
+
+            w.setOutput(ios);
+
+            ImageWriteParam p = w.getDefaultWriteParam();
+
+            ImageTypeSpecifier t = ImageTypeSpecifier.createFromRenderedImage(img);
+
+            IIOMetadata m = w.getDefaultImageMetadata(t, p);
+
+            String nativeMetadataFormat = m.getNativeMetadataFormatName();
+
+            Node root = m.getAsTree(nativeMetadataFormat);
+
+            IIOMetadataNode textEntry = new IIOMetadataNode("tEXtEntry");
+            textEntry.setAttribute("keyword", "comment");
+            textEntry.setAttribute("value", "This is a test image for JDK-6945174");
+
+            IIOMetadataNode text = new IIOMetadataNode("tEXt");
+            text.appendChild(textEntry);
+
+            root.appendChild(text);
+
+            m.mergeTree(nativeMetadataFormat, root);
+
+            IIOImage iio_img = new IIOImage(img, null, m);
+
+            w.write(iio_img);
+
+            w.dispose();
+            ios.flush();
+            ios.close();
+        } catch (IOException e) {
+            throw new RuntimeException("Test failed.", e);
+        }
+
+        baos.flush();
+
+        byte[] data = baos.toByteArray();
+
+        adjustCommentLength(Integer.MAX_VALUE + 0x1000, data);
+
+        return data;
+    }
+
+    private static void adjustCommentLength(int v, byte[] data) {
+        final int pos = getCommentPos(data);
+        data[pos + 3] = (byte) (v & 0xFF);
+        v = v >> 8;
+        data[pos + 2] = (byte) (v & 0xFF);
+        v = v >> 8;
+        data[pos + 1] = (byte) (v & 0xFF);
+        v = v >> 8;
+        data[pos + 0] = (byte) (v & 0xFF);
+    }
+
+    private static int getCommentPos(byte[] d) {
+        int p = 8;
+        while (p + 8 < d.length) {
+            if (d[p + 4] == (byte) 0x74 && d[p + 5] == (byte) 0x45 &&
+                d[p + 6] == (byte) 0x58 && d[p + 7] == (byte) 0x74)
+            {
+                return p;
+            }
+            p++;
+        }
+        throw new RuntimeException("Test chunk was not found!");
+    }
+
+    private static BufferedImage createTestImage() {
+        final int w = 128;
+        final int h = 128;
+
+        BufferedImage img = new BufferedImage(w, h, BufferedImage.TYPE_3BYTE_BGR);
+        Graphics2D g = img.createGraphics();
+        g.setPaint(new GradientPaint(0, 0, Color.blue,
+                w, h, Color.red));
+        g.fillRect(0, 0, w, h);
+        g.dispose();
+        return img;
+    }
+}